I have to say that while I understand the complaints oft he OP, I do not understand the intensity with which they’re presented.
I could list a number of features I think absolutely should not be in the game, but as long as they are unlikely to ever affect me, they’re minor, they either matter only in a context separate from the game or in a theoretical context. So it’s a waste of enery to get worked up about them, most of the time.
Take multiclassing. For me, a class is part of a character’s identity. Characters have a certain class because they like doing the class-typical stuff, not just because they can. To change a class means to change who they are, and so most likely I’ll never multiclass anyone, and I’ll argue that multiclassing NPCs means devaluing who they are. In Terms of rules, IMO there should be some class-independent skill choices – for instance, I think you should be able to upgrade the skills you get from your background regardless of class, but not more than that.
Now Larian has chosen to be more free about this. Do I like it? Not so much, and in the proper context I might get a little passionate about it too,, as about the identity thing that has been discussed elsewhere. But it matters for my BG3 playthroughs likely not at all, so why the heck should I get worked up about it in the context of discussing this specific game?
One feature I’d like to single out, because I most emphatically disagree with the criticism, is races and attributes. From a viewpoint of verisimilitude, what is a race in the context of Faerun? A fitting description could be something like „a group of people with distinctive physical features, and distinctly distributed attributes and abilities, on the whole distinct enough that they maintain a common physical identity, and sometimes, though not necessarily, a commom cultural identity, by rarely being attracted to people of other races, thus rarely interbreeding with others.“ „Distinctly distributed“ means that the game rules, as much as they do not allow variation, describe typical features, not necessarily universal ones. A half-orc with low STR would be uncommon or rare but not non-existent. From this viewpoint, more variety in attribute distribution sounds plausible to me. In essence, I think any rule change that allows to choose a race for roleplaying, as opposed to roll-playing, is a good one.
In general, IMO the rules exist to facilitate co-operative storytelling. Roleplaying games are not competitive games, where it matters that everyone plays by the same rules. I see many players bringing a competitive mindset to these discussions. I think that is not appropriate. Many of us like the occasional challenge, but rarely do we like the same kind of challenge, and some do not like them or don’t have the the time to deal with them. Rules that restrict everyone should facilitate as many playstyles as possible – even those with which you do not agree. There is a difference between „this is not appropriate“ and „this should not be allowed“. If you want to be competitive, that’s fine. Find a group of like-minded players, but do not attempt to impose your standards on all.
And if you allow me to get a little passionate: I couldn't care less how strictly Larian sticks to any particular ruleset. I've GMed roleplaying groups for decades and really, rules as such do not matter. The stories matter, the actions of characters matter. Rules exist for the sole purpose of making it feasible to make non-arbitrary decisions about the actions of characters and their outcomes in a world that is in reality more complex than any ruleset could ever encompass. CRPGs are by necessity more limited than tabletop roleplaying groups, but those limits are not a virtue. They're a necessary evil.