You could say that in a way - Solasta is a perfect demonstration why Larian has worked so hard to try to balance encounters by doing homebrew mechanics for creatures. Making sure that the mobs have as many tools as possible to work with so they don't end up - for example - being a dumb flying creatures that's only move is to move in and out of range before/after it attacks - setting itself up for multiple opportunity attacks and allowing it to get hit with persistent aoe spells like Spirit Guardian.
It gets to the heart of the problem with video games - no human DM to allow for creative behavior/schemes/attacks. So you try to come up with other ways to express that behavior.
I hope Larian fixes all the exploits, 100% I do. I want BG3 to be even more challenging than it is and I don't want anyone to have an easy out unless they choose "story mode". Solasta may get the technical stuff right, but Larian does a much better job of making the encounters feel up to the appropriate challenge level of D&D.
I am actually in slight agreement here. BG3 can still be hard without needing to pigeonhole everyone into believing they need to cheese back harder, just because enemies have access to the same overpowered mechanics too and that encounters may be designed around the cheese existing. DOS2 already proved this somewhat, with that game's problems solely revolving around the armor system and the stat bloat it encouraged the further you got into the game, rather than anything mechanical. Sure, DOS2 had problems with late game bosses playing one-shot rocket tag with your party, but it's a very different problem and the distinction is quite important there. BG3 can absolutely do away with stealth, backstab and high ground shenanigans, and the main things that would result in is some high-ground heavy ranged fights being a lot less ridiculous.
And again, backstab advantage would have no reason to exist if shove gets the second half of its function implemented, the option to knock things prone so that all melee attacks against them get advantage until the target's turn. Granted, enemies can probably shove YOU prone too. But it'd be a lot more interesting than out of bounds instant kill shoves, because I gotta say, that Druegar fight where the boss shoved Gale off the ledge (and his decaying corpse subsequently killing Scratch back at camp) as the final fuck you towards the very end of a fight that took me about half an hour was really not what I'd consider legitimately hard or compelling. It left me upset enough the first time I played through that I just went into total no mercy mode after reloading and straight up stealthed and shoved off as much of the camp as I could, and had my Bard/Gale/Wyll spam Shatter nukes on all the remaining survivors, ignoring all the precious potential for dialogue from the boss and loot from everything I threw off. Pulling that off wasn't hard, and this wasn't some crazy unique mindblowing tactic or anything, it was just cheap. Doesn't compare to, say, using teleport to pick up those water barrels in the Blackpits and drop it at the top of the platform so that it becomes much harder for those void slimes to necrofire everyone's asses up there.
It is questionable that one of the most efficient ways to play the game is to avoid dialogue entirely and stealth/alpha strike everything, which is the antithesis of Larian putting so much effort into the writing and cinematics to begin with. Or send one party member to act as bait while the rest of the party sets up. Makes me feel
extremely murderhobo-y, and I have enough problems with that in my tabletop group as of late. But really, if the game wants to play with cheap instant kill stuff in some fights instead of actually being legit hard, then it should be expected that some players may decide to play in a way that doesn't respect the narrative half of the game either. The part of the game that Larian is clearly putting the most effort into, and the part that no other cRPG can really touch in the visuals department.
That said, your example about flying enemies only possessing melee attacks is a deliberate thing. They're there to provide value to ready actions and force melee characters to play defensively and predict. BG3's current systems generally promote heavy offense, because there's really no playing defensively to speak of, with the high frequency of AoE thrown items and field damage with no saving throws to avoid them, height advantage existing, and the kind of action economy that's present as is.
Even though I advocate for the addition of ready actions and dodge actions, it is also important to question how much the latter would actually matter in the context of how BG3's AI behaves. Maybe not as much as it does in Solasta, but more options are always better than less in the long term. At the very least, it means your melee can hold their ground to punish someone trying to climb up to reach your ranged on high ground, instead of hopping off to chase them and potentially expose themselves to retaliation from other enemies at the bottom, and the dodge action will at least allow any character that otherwise has no viable tactics to defend themselves by imposing disadvantage on everything making attack rolls against them until an opportunity presents itself.
I think smarter enemies could potentially ready action and dodge action against YOU as well within BG3. Wouldn't that be neat? I don't think Solasta's enemy AI actually does this... Plus we all know we're going to get fireball'd out the ass after Act 1 of BG3 since this is a Larian game we're talking about, so having proper reactions so we can actually control our counterspells is going to be pretty damn critical. Because it'd be such a shame to blow that counterspell on a cantrip only to end up letting that fireball go through, one that may force you to reload the game. Much bigger waste of time than any prompts asking you if you want to use a reaction.