Case in point firebolt having a smaller damage die, but causing things to burn. So it's 1d6 now vs. 1d10 a difference of a 1d4. It's a slight buff I've not seen any massive numbers off of burning normally within the 1d4 range. The flame also doesn't last long usually 2 rounds, which is 12 seconds D&D time. on average your still only getting 4 extra damage on an enemy. Since the burn doesnt stack, then your next firebolt will still only be 1d6 worth of damage. plus on average an extra 4.
If they simply stuck with a nongraphical games listing of spell effects then it would be boring. I know DM's that house rules things like using fire in a forest has a chance of starting a fire. It adds more realism, and consequences to the game. Makes you think, instead of going murder hobo all the time.
I think the buff to firebolt is massive. It often applies damage three times to the same target. They get hit and ignited. And when they move, they get ignited again. Not only that, but you still apply damage when you miss in most cases. Ray of frost combining a trip with decent damage is also a massive buff.
And I don't think the surfaces add any realism. Getting shot in the chest by a frostray, and suddenly slipping on ice seems weird. The same goes for the cobblestone beneath your feet getting ignited from you being hit by a fire. I don't mind stuff like grease being set on fire by flames though. Many a player would ask their GM if they could do such a thing.