I don't play TT 5e, but page 242 of the DMG addresses the issue of saves and ability checks, discussing not only critical success/failure (extreme outcomes), but also partial success/failure, and marginal success/failure. The notion is to encourage DMs to consider a continuum of outcomes and complications. rather than always apply simple pass/fail absolutism, which is not always a satisfying experience for players.
Would you consider Larian implementing auto-fail and auto-succeed for ability checks and saving throws to be "considering a continuum of outcomes and complications. rather than always apply simple pass/fail absolutism" ... Because I would not.
Depends how you look at it. D&D mechanics are generally an exercise in simple linear arithmetic; a collection of + and - values, summed with a die roll, compared with a taget value determining pass/fail. To me, that is "simple pass/fail absolutism".
Anything diverging from that is a nuanced (non-absolute) result. So, advantage/disadvantage, or critical pass/fail, are both nuanced outcomes that diverge from the linear norm.
I am not aware of any base D&D mechanics that deal with partial or marginal success. It would be possible, but tedious, to detail a selection of outcomes for each occasion where a check ( combat and non-combat ) is needed, but over the years it has been easier for TSR/WotC to just give wooly advice ( as in the DMG p242 mentioned above ), and make it the responsibility of the DM.
So, in answer to your quesion; no, I would not say Larian have considered a continuum of outcomes and complications. They have just copied the WotC 5e ideas and implemented only the easy non-linear behaviours ( advantage/disadvantage and critical ), without any actual variance in the outcomes.
My point ( as much as I had one ) was that I don't see Larian's implementation as being outside the scope or intent of 5e, as documented, even if it is not as elaborate as it could be. You, on the other hand, seem to be suggesting that their implementation must be changed, even though you did not explain why this is so.
Pass/Fail absolutism seems to be entirely what they build all of their decision trees and dialogues around, currently, despite their claims to the opposite. Categorically, you're faced with a situation, and you can "do nothing" or "Not try" and see, guaranteed what the fail state outcome is... or you can "try to do something", and either succeed... or fail, and see the same failure outcome as if you hadn't tried. That's it. That's the entirety of their outcome mapping. They are not making-failure-fun, currently.
Yes, unfortunately, that is largely true, both of this game, and almost any other current game. Most game dialog systems are quite crude, usually allowing a few "flavour" interactions based on character attributes, or perhaps easier/bypassed checks.
Relatively few games have many interactions of world-altering significance, because an interaction-based world-state is very difficult to manage unless the story-line is quite linear.
As with many other games, BG3 seems ( at present ) to have a single major game-path choice, a selection of faction-approval choices, and a selection of incidental choices to gain advantages.
This is not particularly exceptional in EA, although we can set up quite a variety of future content for Acts 2/3. I am sometimes optimistic that Larian are knitting together a truly labyrinthine plot, but realism and experience suggest that is unlikely; partly because the development cost and difficulty would be high, and partly because a lot of the audience seem to care more about combat, and don't want the story to be complex.
