waveclear is important mid, because when you can shove better, you get priority over your laner when it comes to roaming and skirmishes or invades. Or you can get visions, or poke them under turret.
Also, if you can 1 shot the casters, then it becomes very dangerous and hard to punish a ranged champion last hitting melee minions. Easily ganked and you basically have to use your own abilites on minions to not get shoved into turret.
idk how rito wants to fix/change this, but that's some reasons why waveclear is important mid :P