It's a game, not a simulation. I personally don't like a lot of the new changes but they are entirely within WoTC's wheelhouse to make. If it better fits their philosophy for the game then they are going to do it.
As for the games and Larian's autonomy, I personally think the contract was pretty fine-grained. Larian could easily have had complete autonomy with regards to the story and many aspects of character but could also have been required by the contract to follow changes to character creation rules. The devil is in the details and we don't get to know those details.
