Surfaces just screw everything up and make every combat a predictable mess of everything burning, everyone slipping on ice and barrels exploding.
Mobility that's added? Well, it doesn't really matter since every battle is pretty much centered around who can reach the high ground, so you can have all the mobiity in the world, but if you're playing a melee-centered character and you have to run up fifty stairs or huge hills every time goblin archers get advantage on you with the Larian ruleset, mobility wont cut it.
As for the bonus actions, they take away from classes that would otherwise be uniquely equipped with those abilities, like rogues.