UI and Party controls hardly has anything to do with DnD 5e though, you are muddling together two topics I feel.
I totally agree that Larian needs to read the Players Handbook again, and all the spell rules, and make the game like that first, then see where they can add the "Larian flair". While I think the game feels like DnD and not DOS2, the game feels like it was adapted from DOS2, and they haven't adapted all the functionality yet.
The UI has everything to do with D&D, because its job is to convey all the elements and information of the game's ruleset to the player in an effective way. Party control is important for any CRPG, D&D or not, and is a fundamental element of game design that should be designed around the needs of the game. Currently, the UI doesn't coveny 5e D&D well at all and the party controls make playing the game a chore. These issues are especially irritating for somebody who has seen both done far better in CRPGs for the last twenty years (including the two previous games in the series BG3 proports to be a part of).
I'd be way less worried about this is Larian's last two games hadn't used very similar UIs and basically identical control schemes, which makes me think this is just how they do things and not a crude first effort for early access that they'll continue building on.
