Sorry to break your heart, but a lot fewer people would be taking this game seriously on a competitive level if every single one of your given moves had a 20% chance and below to do nothing. Part of what makes Pokemon such a competitive strategy game is the choices we make when building our teams. If you're tired of your moves missing, you can change your options to accommodate your need for reliability. Even in a game like Pokemon, you need something to count on.Please don't extrapolate from one to infinity. More luck based =/= unplayable.
But I'm drawing the line at letting Garchomp get away with this free evasion nonsense. It's so arbitrary and gamechanging that it's disgusting to think how some people are randomly losing their matches to an endgame Garchomp thinking "Well, that's ok. Let's see if I hit him next time." I've seen this happen far too often on both my end and my opponent's end to think it's fair. Maybe if Sand Veil halved his attack or something, it wouldn't be such a problem to miss every once in a while.