You stated that Barrels are present in game, and teoreticaly could be used anywhere ...But they are not present in "every encounter" as you said it, they have to be carryed to those encounters (maybe except Gut, and possibly Ragzlin that is pretty close, but for both there are much easier tactics) ...
That is why i just cant accept this argument. :-/
If you were right, and there were coventient Barrel of gunpowder next to every, or at least half harder boss encounters ... i would agree with you, but they simply are not. :-/
If you drag them there, use them, and then feel like your game was just ruined, its not misstake of that barrel ... even less if you do that again.
You stated, that Barrels are seen as "an optimal strategy" ...But that is also not valid ...
Actualy by using them in Tutorial, im prolonging the thing that can be done in less than 10 minutes to almost 3/4 hour ... and as i said multiple times, so far i never managed to kill all 3 cambions with that explosion allone, so all i did is shorten the combat, therefore the "optimal strategy" and "easy button" is not even working properly here

... that dont seem to be price high enough to pay?

If you have seen
Wolfhearts video of Him vs. all Goblin leaders, he also used some explosives there ... preparation took him almost whole hour (shame he cut it so it cannot be seen, not sure if he record his streaming) ... and we all should know that he could kill them "convencial way" and funny enough, in this particular example it again would ben even easier.

I dont have data for any other encounters, ince i didnt use them there ... if you have any screen or video, please share.
You stated, that amount of Barrels is "immersion breaking" ...I never counted them ... if you did, again, please share.

My gues is aproximately 20-25 ... wich for whole map, with two levels and 21 potentialy challenging encounters (meaning: Ruin looters outside, and inside, attact at Gate, fight by windmill, Wood Woads, Red Caps, Masks, Hag, Gut, Minthara, Ragzlin, ...theoreticaly we can count outside of Goblin camp as another..., potentialy Ogres, Gnolls, Githyanki patrol, Spider matriarch, Minotaurs, Bulette, Hooked Horrors, potentialy Myconid Willage, Duergar slavers) isnt so much in my opinion. O_o
You can notice i leaved some, since i concidered them the most trivial fights ...
I know, most people using this sentence is not actualy talking about numbers, but about that in some DnD rulebook (or w/e you call them), there is told that "
Gunpowder is rare" ... please note, that even if you multiplied the amount of gunpowder by a thousand ... on a global scale, it could still be quite rare. :-/
You stated, that you are not sure if game is "balanced aroung it or not" ...I honestly dont understand this statement, and im affraid i never will ...
How exactly could be game "balanced around something" you can completely avoid and ignore? That dont makes any sence to me. :-/
I dont know how you define balancing ... but for me, balance any system "around something" means expect the players to use it every time ... and therefore adjust the game to the power level the player would achieve if he would use it every time.
If Barrels are as strong as you claim, that would mean you all who dont use them were playing hardcore version, and you were never suppose to manage to finish it. O_o Do you really believe that is the case?
You stated, that you feel like "your choices dont matter" ...All i can say for this is: What about the choice not to use barrels?
Im sorry, existence of Barrels make you feel that ... i really am. But my sympaties is actualy the only thing i could offer you, since i simply believe that by making this *choice* your other choices would start to matter again. :-/
This is some(other)thing i just dont understand ...
If you really see Barrels as such cheat ... how about actual cheats in other games?
Is their existence ruining your experience? Does bother you that some guy, or kid in other side of the world is using cheats to make his character indesructible, and his weapons so powerful that he kills everything on map by single shot? ... Or do you just play your game, enjoy your encounters, and dont care at all that developers actualy had to implement those cheats in that game, since they do not appear on their own? :P
That is why i say: To live, and let live.
You stated, that "using barrels in every battle is boring" ...I agree ... and that is why i dont do that.
Why cant you? O_o
Why the very existence of that option is bothering you?
That is what i would like to understand.
You stated, that "the amount of it feels like a DM constantly telling you to use his "fun" solution" ...I have no idea what to tell you ... you are focusing on problem that dont exists, and that is bringing you this experience. :-/
Its sad, but you did this yourself. :-/
You stated, that you see "an oil barrel around every corner"I believe i allready reacted on this statement allone ...
By listing all places where i remembered Barrels ... i cant find it so lets do that again:
- Single explosive in Nautiloid remains ... prepared there obviously to overcome this specific encounter for people who are still level 1 ... fun fact: this is actualy
the one and only Barrel in whole Act 1 (meaning except Tutorial) that actualy fits to all your descriptions.

- Single Barrel inside the Crypt ...
- 3 Barrels in Druid secret passage ... part of the trap set to protect the chest
- Single Barrel in entrance to Blighted Willage ... part of the trap, prepared by obviously ambushing Goblins
- Few (dunno, but certainly less than 5) in Blacksmith basement in Blighted Willage ...
- Dunno how many in storage-room in Selune temple (aka inside goblin camp) ... yes, there is many of them, but it have RP purpose you can find, when you listen goblin talking, all of them was bringed by Zhentarims.

- 2 Barrels in Halsin vs Goblins encounter room ...
- The secret passage to Gnolls encounter ... there are 3 if i remember corectly and they are set there as part of trap.
- And finaly Zhentarim hideout ... there is also quite a lot of them, on many places ... but since Zhentarims werea allready confrimed as group that is able to provide explosives from all around the world ... it kinda makes sence to me, that they will also use them. :-/
I dont remember any more ...
As far as i know, for example Underdark is free of them completely ... there are only flamable mushrooms, but you cant drag them anywhere.

It might seem a lot at first sight ... but its not even half locations in game. :-/
Maybe not even third ...
So i would say that "around every corner" is a little too dramatic. :-/
You stated, that "its hard to ignore"I simply cannot agree with this ... probably never.
Since i played the whole game multiple times, and i did ignored it COMPLETELY (read as: Never blown even single Barrel) ... so either im exceptionaly good, or it obviously IS not so hard. :-/
My money goes on second option.
You stated, that "Larian has a tendency to put in so many exploitable mechanics that aren't glitches, so you start wondering if you're supposed to use them, especially if you're having a hard time in a fight."I didnt find any way to shorten this sentence without loose its meaning ...
I would say for this that this is first objectively good argument (in my eyes ofcourse), that i would agree on with you ... except that i dont care what Larian expects me to use, what i care is what i want to use ... and one of points of existence for Early Acess is show Larian what we wants to use, and if this game would even be playable for us while we use that.

At least, that is my point of view.

And since Larian keeps tuning all encounters based on what people do, and what people dont do, and where people have hard time, and where people dont ... i dare to say that im on right track.
You stated, that "people (even those who hate it) actually do want to use barrelmancy"It certainly dont feel that way.
You stated, that "but they want to feel clever for using it and it should be unique to a certain experience."And i say they have that option.
You stated, that "this means making it more rare and as they've done add some sort of requirement for strength, because then your character choices matter again."Requirement of strength is allready there ... its existence BTW, is the main (and possibly the only) reason for existence of this topic.

And about rarity? Every player have option to make this experience as rare as he pleases ... it all in our hands. :-/
But im repeating myself again. -_-
And finaly ...
You stated, that "If it's too easy to do, it simply becomes a thing they won't allow themselves to use or it trivializes everything, rather than a cool option they could use once."If they won't allow themselves to use it ... even tho they want to, and the fact that they didnt ruins their game ...
I would dare to say that they made wrong decision. :-/
As i said million times, and as i still keep believe:
Its all in our hands ...
You want to blow none Barrel > you can.
You want to blow single Barrel per game > you can.
You want to blow all Barrels in game > you can.
And THAT is the right way to do ... give us options, let us decide.
I thank Larian, for understanding this.