I think BG3's main problem was its story being sabotaged by its design (or the other way around, however you like to look at it).
The initial motivation was "You have a bomb in your head! Hurry!" - but then, the game is designed in a way, that you can completely go off the rails and ignore everything. So the tension is entirely lost.
I think that story setup is not a good fit and - this is my little conspiracy theory - I feel like the writers realized that as well. That is why they introduced all kinds of retarding elements.
The remaining story then takes forever to go anywhere - and where it goes is not that interesting. This is the reason why I eventually quit after almost 50 hours (consider, you can easily read a 1000-page novel in that time - so I think it's fair to say that the story about a big meanie who sits in a tower is kinda spread thin over the playtime up to that point).
I will probably pick it up again and finish it, but it will be for the mechanics and encounters - which are pretty fine I think (and also the reason why I played for 50 hours, exploring most side content).
As for the OP's idea that classic RPGs were already ideologically aligned with what you see in BG3: Well, maybe, but they were still better executed in terms of writing.
Arcanum is actually a good example because its story setup is a better fit for a freedom-oriented design ("Here's a ring and a kooky prophecy, now do with that whatever you like").
Same with the original Fallout, where the "bomb" isn't ticking in your head but in the vault, and if you twiddle your thumbs and do nothing it punishes you for it. So the design actually aligns with the story. Which was not so well received, but at least it's coherent. Maybe that's the problem with BG3's writing. It wants to have its cake (the freedom to do anything, however long you like) and eat it too (the tension of a time bomb). At least as far as structural problems go.