Rather too many people here getting frothy over changes from core 5e rules. Larian do their own version of 5e rules. Elemental surfaces are fun, make the map layout and positioning absolutely crucial, and allow for much more tactical play. Some people get hung up on minute differences from 5e: maybe enjoy the game as it is, if it doesn't work in the game, then critique it in those terms. 5e isn't a bible and it's not useful to be fundamentalist.