Not sure why you're talking about "mechanics" (I understand it as sequences).
The same "mechanics" (fall damages because that's what you're talking about) are everywhere in the game.
The boss is balanced arround Larian's homebrew like any other combats and you just have one more solution to deal fall damages with webs.
You're just railroad to use Larian's mechanics more because it's a harder combat but every combat in BG3 has the same "sequences". This is absolutely not specific to the spiderqueen or destroyable webs.
You just struggle "more" here with a party of 4 if you're playing with your own tactics but you can also solo'd it easily if you use BG3's "right OP sequences". Like any other combats.
I think you're talking about mechanics of "pushing", it's different. But I agree with you, "pushing" mechanics arise too often. Because wherever you have a difficult fight, there is an "abyss". At least that was in fight with hag, spider, and minotaurs. This mechanic won't work with beholder and bulet. And you can also fail push, and then game will punish you like it was on Larian stream.
I don't think this will be changed, even if the design of these locations implied ability to push enemy.
But you still have options, Larian doesn't take that away from you, that's what I'm talking about.
Options to struggle on this combat during 4h ?
Option to OS the boss rather than 2 or 3 shots him ?
Option to use the win buttons because finally it's too complicated if I don't ?
Balancing / optimizing combats arround all these mechanics whatever we're talking about fall damage with push, fall damage with webs, fall damages with thunderwave, easy advantages, dipping, free disengage and so on DRASTICALLY reduce our options.
Using Larian's OP mechanics or struggle for hours is not what I call "options".
1) Starting point : creation of OP mechanics for the player (fall damages / push is one of them)
2) Consequence : combats are too easy if you use the cheese
3) Solution : creation of OP mechanics or stats for monsters (rage, multi attack, minotaurs jump, consummables,...)
4) Consequences : use the cheeses or it's gonna be very hard/impossible. How many players complained about the game's difficulty...?
4.1) Unexpected consequence : cheeses are SO OP that we finally don't need any lone wolf mode... Maybe the game should be harder ?
BG3 won't ever be better balanced if they don't rework the starting point. Every combats (and it's even more obvious for harder/unfair/frustrating encounters) is the results of design choices that leads to changes that leads to more changes,...
To the point that I 100% disagree with you : we don't have any options other than playing how devs wants us to play. Sad in a tactical TB game based on D&D.