Staying true to the 5e rules will kill this game. The game is too ambitious for something like this to work. They can't afford to ignore DoS fans and casuals. Ignoring these players will lead to a sales disaster. Unlike Solasta, I doubt BG3 will be able to do enough on D&D fans alone.
Some changes like lowering ac and increasing HP are due to turn-based combat. The changes to the shove and dip are here to give the character more to do on their turns. The surfaces also mainly serve to diversify low-level combat. The changes in rest also seem to be due, although it will definitely be changed in some way. The game has a few broken mechanics that should be fixed sooner or later, but most of them shouldn't be removed just because they aren't in the basic rules (most of them can be fixed by proper tuning). I don't see a problem with some people not liking it, but I'm afraid a lot won't change. It seems to me that a lot of problems with the game would be solved if we started from the 5th level but there is no chance for that.
I just don't understand people who want more and more annoying mechanics even though such things don't work well in games (or aren't liked).