Then your point has ben expressed poorly ...
you either learn the gimmicks and defeat enemies easily or you get pounded by the enemies and have to save scum until you figure out what the gimmicks are
having to find just the right gimmick to win.
See?
In both cases you claim that you NEED to use them in order to win, and THAT as i said:
claiming that you "having to find them is the only way to win" is simply not true.
Is false.

---
Now for the rest ...
The gimmick in the hag fight is "unless you stealth around Masks, in wich case those two encounters happens at once and that is BRUTAL..." In other words, unless you do something that is really quite weird from a story perspective - or is really only possible because of janky stealth mechanics - aka long rest and/or sneak around Masks and/or whatever you must do so that both encounters don't happen at once - both encounters together are BRUTAL.
This has ben twisted so hard im surprised it didnt died and fell off on its own.

I thought you have seen Hag's Lair. O_o
But just to be sure ...
> You enter, meet few poor souls cursed in various way ... you get through her magical door ... and then there is a room with 4 people wearing masks, that keeps them under Hag's control ...
Now you can sneak past them, by abusing "janky stealth mechanics" as you said indeed ...
But you can also use Protection from Evil and Good on yourself and wear the same mask from the first room ... in such case they will concider you as one of them and will not attack. > You get past them, no gimmick included, perfectly logical from story perspective.
You can also simply kill them all, wich kinda makes sence since they are in your way and they are hostile.

> Then you get futher into the lair, you get through some posion/explosive/fire traps ... and you finaly arive to the "room" (for lack of better term) where Hag herself is.
Now you fight ... and she can either fight alone, or (if you were foolish enough to let them live and concious) she summons her Masked friends to help her against you.
In other words, you just "used janky stealth gimmick" (to use your own words) to make your fight aproximately 4 (one per mask) times harder.

So ... if anything, this particular example certainly dont proove any point that gimmicks makes the game easy.

Also, since that is just twisted quote from my example, i did that on purpose, in one of playthroughs i decided to try save as much souls from Hag as possible, so i surpassed the mask by using the spare mask.

And it backfired as angry ram.

But at least the fight was challenging once again. :3
Sometimes i wonder if she would summon Red Caps aswell if i let them live ... maybe i try it some day.

Were they gimmicks or legit strategy?
You tell me ...
Every time she duplicate, i simply use Magic Missile ... one dart per every single one of them and they *poof* away.

Mostly those clones dont attack even once.

But yes, i admit sometimes i prepare in advance for this fight by giving
The Sapphire Spark to Lae'zel, or Shadowheart, before i go there.

Either way, in order to beat the hag, you can't just face her upstairs with the redcaps, face the Masks and then face the Hag and win all in one story arc, no long resting, event - well, I suppose you COULD
Ben there, done that.

When i knocked out by non-lethal attack Marina's Brothers ... and then find out that if i long rest, i find their corpses in the swamp ... i was determined to spare their lives, to see if the game will respond in any way ... if i get the option to tell Marina that her Brothers were searching for her, and i beated them, but they should be alive and well ...
Sadly, no new dialogue option showed up ... i just finished the battles with no reward for my extra efford ... it was disapointing.

but the fact that it is BRUTAL means that it is a bit too hard.
Challenging ... yes.
But not brutal, not at all ... since you have peace time between those fights, you can fully heal yourself ... scrolls substitued missing spellslots quite well, and since i was only level 4 their (obviously corect) lack of upcasting was not an issue.

The hardest challenge on that for me was to keep going ...
I could easily say "nah, screw this shit" any time, and just get out and rest.

But i didnt want to.
Anyway what i say was brutal was fighting Hag and Masks at once ... no in between single Long Rest, AT ONCE.

Like both in single encounter.

It's weird that she just waits for you to leave her lair, long rest, and then return full strength to fight her
I dont think its too weird ...
I mean concidering her speech if you get there is that she is comfident that you have no chance to beat her after all. O_o
Also you say "wait until you return in full strength" ... from "story perspective" she could easily presumed that you lost interest and leave ... but surprise surprise, you returned next day.

and it's weird that your entire party can sneak past the Masks the way they're positioned unless your party is REALLY good at sneaking. Maybe Pass Without Trace might make it believable, but especially if you're trying it out with people wearing armor with Disadvantage, stealth should be next to impossible in that area.
Its actualy not so hard if you really want to stealth through ...
When you enter the room, first wall on your right is low enough so most characters can jump on it ... then you send your best sneaking agent (prefferably improved with some buffs) forward to extinguish the torch ... so masked HUMAN loose most of his sight ... and everyone else in the room stands behind some wall, or pillar ... so your party simply climb down and rush towards the waterfall.

You dont really even need turn based mode to do this.

But if you would demand stealthing through while not abusing vision cones ...
Well, basicaly all you need are 4 potions of invisibility.

Wich is no problem to get by that time you reach this point.

But again, stealth being the way it is, that is just a gimmick to be exploited. Sure, all fights are easy if I exploit the stealth system. I could wipe the Masks, and have, using broken Stealth.
That is for example one of gimmics i never ever used.

Reason is simple: It seems boring.

//Edit: Oh now i see that huge quote isnt actualy a quote.

Well, i gues i should read it aswell ... expect another edit with reaction. :P
That was my whole point.

You are the one who said you "need" to use gimmicks in order to win ...
If its "of course possible" without it ... then you dont "need" to do that. :P
Dont be mad at me ... that is just how the word "need" is defined.

Maybe it took you one try each time. Good for you.
Dont remember actualy, but im sure i made some bad decisions leading to my death between all those games.

So certainly not each time.

I thought, "Okay. Roleplaying my character, he was a cleric who was ready to support Lae'zel if things went wrong. He and the others were nearby so they could have her back. But I tried to position myself well ahead of time. Battle started, as I expected, and the Gith won initiative and killed Lae'zel in the first round before she could go. Then they Misty Stepped to my cleric and wiped him also (or sniped him with a crossbow from a distance). Cut my party in half before I could even take a turn. Had to reload like 8 times before I finally beat it.
Well, tough luck i gues. :-/
Funny enough, i still remember my first encounter with them ... back in those times you probably remember Lae'zel leave your group and run toward other Githyanki ...
I thought, roleplaying my character: "Okey. Someone should probably go with her and make sure everything will go well ... on the other hand i allready heared from Zoru that they are merciless killers, Kithrak just said to Beretha "question, kill, then move on", and they just killed bunch of people just bcs they could ... so you two, hide here and wait if something went wrong."

You know what was best? My warlock managed to persuate Kithrak to use her services in search for the weapon and no fight happened at all that time.

Second time i was there i rush with my whole group, confident that i shall once again talk out of it ... well, i didnt ... and i can asure you that they wiped the floor with my party.

But i get there unprepared, wounded, exhausted (meaning low spellslots) etc. so that was no big surprise.

Since then i usualy hide two of my group up there "in case something went wrong" ...
I dont even remember when i decided to challenge myself and kill them with whole party starting on the ground ... i used misty step on start of the fight to get some distance obviously, but not to the top of that bridge.

I dont deny that i came prepared, i had (almost?) everything done from the surface (i never go to the Underdark first) Gale had few Shatter scrolls (3 i think) so he can keep on pushing after spellslots will be out, wich also helped a lot ... and i buffed my party properly before the battle started.
But in my own eyes, i managed to kill them fairly. :3
That's the normal experience I still have to this day. Unless I use the gimmick and go to the bridge, or unless I win initiative, or I shove several off the edge using insane shove distances, it's pretty much game over. Might as well reload.
Have you ever concidered that you do something wrong? :-/
You should not design your combat encounters so that if you lose initiative it's pretty much time to reload. That's too unbalanced and volatile. If bad luck comes your way, you should have a harder time winning, but you shouldn't necessarily have to reload.
I get it you have bad experience ...
But im still convinced that they are not what are you describing ... based on for change my own experience.
Yes, Githyanki fight is hard if you start on same level as them ... but no, it is not impossible and no, its certainly not "necessarily have to reload". :-/
and if I play through smartly, I don't have to reload.
I really dont waant to be unnecesary harsh here ...
But concidering that we "know" each other for almost a year now, and concidering that i have seen countless description of what you concider "play smartly" ...
I dare to say that your and mine ... and as it seems also your and Larians ... image of smart play is just different. :-/
Again, Solasta has done this so very well. My current game, I haven't even died once. Not a single character has died. Several times, they've fallen and I've had to use magic or a potion to revive them in time before they die, but none has died and made me reload. Combat encounters are challenging, and sometimes I've thought, "Holy crap! I'm going to lose this fight and I'm going to have to reload," but then I find some way to turn it around and win.
Eh ...
I gues i should skip this coment, since im missing important context.
But we both know that i dont do things just bcs i "should".

So one thing i must say ... i dont think that "one person being able to get through some game smoothly and without any problems" is in any way showing how well is that game done. :-/
At best, it certainly shows how well this game fits that particular player ... but hardly anything more.
It's not so hard that I'm having to reload a dozen times to find a way to win or to just get freaking lucky and win.
You know saying it like this ... it almost feels like every time you die in the game, you simply reload and go do exactly the same expecting different outcome. :-/
Once i did something simmilar ...
Just for the lols, i decided to "solo" Demon General on Nautiloid ... so i created Fighter Dwarf 17-14-17-something ... i steal Lae'zel armor, i get Shield and Battleaxe ... Shadowheart gave me Protection from Evil and Good ... and we get to fight ... cleared first part of the room ... killed Illithid ... then i moved girls somewhere safe, Quick Save, and started my duel ...
I died in 3rd or 4th round ... quite embarasing, but RNG is a bitch.

So a loaded ... and then it hit me ... i loaded in middle of the fight, exactly at the spot when all was prepared and i just started my duel ... so i decided to abuse savescuming so hard, so even the definition of savescuming would be embarased for it ... and it was not just possible, it worked like a charm.

All i needed was to hit F5 after every single sucesfull hit ... and since my character died on first swing from general, when i loaded (once MC die, tutorial ends) i returned only single turn. xD
It was long and tedious fight ... but in the end, General was dead by nitpicking ony those swings when he missed. xD
Anyway that was just the funny part ...
My point of this reaction is that if *i* die in combat, i usualy try different approach.

Even if things are going wrong, I still might pull through and turn it around.
I believe you can ... and i believe it, bcs that is exactly what i do. :-/