This is, in my opinion, a very important issue. But out of all the things that could be improved in BG3, this is what is going to be the hardest to do... if they acknowledge this problem and aim to rectify it.

The thing is - it's so incredibly difficult to capture a "feel" of a game. People often dismiss this as "you just want an Infinity Engine clone, get on with the times, it's 2020". But that's not what most BG fans want. IE games weren't all the same. Each series felt different. BG and P:T were on the same engine, yes, one could feel some familiarity between them, but they each had their own "feel". It wasn't one thing that made BG "BG". Replicating the game engine could give some nostalgia vibes, but would hardly solve the problem (not that the game engine is a point of discussion, obviously). I believe a game can be both modern and a proper sequel to entries from 20 years back.

So what were the elements?

The story: Larian said the BG3 is a "proper sequel" story-wise and I'm inclined to believe them. I like the whole illithid tadpole plot, and I'm eager to learn more about it and the forces behind it. The main plot both is linked to the original saga (per what we're told) and since the beginning brings familiarity. Illithids have been encountered multiple times in BG2 and there's the recurring theme of "something alien" being a part of the protagonists - it can be embraced or rejected. At the same time, there's a new spin to it. I think the core idea behind the main story is solid.

The companions: I'm a bit torn on this; I don't mind companions initially hostile to the PC (especially that we got the "more evil" ones for EA start), but I expect I'll only like one of them. I respect Larian's "quality over quantity" approach, but having only 8 companions to choose from (as it's been hinted) is a problem. That's about half of what BG2 had, and even there it wasn't a huge choice if you wanted to roleplay your PC and not just pick characters based on one criterion. I think BG2 struck a good balance between quality and quantity. Regarding the companions' "specialness" - I don't mind them being very special, I prefer this to Average Joes. One thing would be that it strains suspension of disbelief that those people with crazy backstories would just by coincidence all be taken by illithids, but it could be explained without much problem, I think. From what I understand, there's a lot to improve about the specifics of companion interaction, however. I've seen a lot of good ideas on this forum.

I agree on the combat system, though, and many "game-y" elements. But still, I don't think it's impossible to have both TB and proper BG "feel". It just becomes harder to achieve.

A very important part - and also hard to capture - would be the "atmosphere", but I won't try to comment on this, not having played the game. From what I gather, it's good, but not reminiscent of the original saga.

All in all, I don't think the problem lies with any particular part; the lack of BG "feel" many people report is probably the combination of many elements that differ from the originals (even if each one is fine on its own) and the execution of specific pieces.

I think we should continue discussing the issue in a constructive way in order to identify the source(s) of the problem and try to come up with good, viable solutions. There's already a couple of threads with good ideas for this.