I don’t think the old UI is that good.

Button layout is unintuitive, menus are massive. The difference between then and now is resolution - one doesn’t need to cover the screen in large buttons to make things readable. And while, BG1&2 base menus are functional, they are not once more options are available. I also disliked how many clicks one had to go through to start playing the game.

BG3 seems to be using a pretty standard modern layout. It looks perfectly fine. With game running on 3D engine, and being able to generate nice background on top of couple buttons... why take the advantage of it?

I don’t think menu is as good as D:OS2 though... the cave BG3 uses as background isn’t terribly meaningful, at least to my knowledge. Perhaps it will change once we have actual Baldur’s Gate in the game?