Yes all fanbases are to one extent or another cross-cutting. But don't you think it is telling that the only fanbase that is near-universally thrilled with this game is the D:OS fanbase ... shouldn't at least some portion of the D:OS fanbase feel like this is NOT their game?
Is this actually the case at all? I can speak for nobody else and nor shall I attempt to, but I would quite like to see a BG game be BG. Will it be? I dunno. Will somebody else be the arbiter of that? Goes without saying, probably for multiple values of "somebody else".
Then again, am I a DOS fan? I'm a Divinity fan. There're things DOS (both of them) does that I like less than other games. But I've taken them on their own merits, which is what I'll do with BG3; and it'll be easier working from the position that it isn't trying too hard to live up to expectations that are rooted in something else.