Answer: Larian could, if they wanted to. But they don't, and there are numerous reasons for that.
The problem is, I have no clue what those reasons could be. Larian doing the other stuff you mentioned doesn’t require messing up the combat system. As far as I can tell Larian just breaks aspects of the existing system for no benefit that I can see.
I am not 5e purist. Most issues I have with combat, were there before I played Solasta or read up on 5e. It’s just easy to point to the other 5e game and say: “see it works better without your interference”.
