So why doesn't Ezreals Arcane Shift....
 

So why doesn't Ezreals Arcane Shift prefer to target champions? Ezreal's skill set encourages maintaining a huge distance except for this one? There are other champs that have skills that focus champs before creeps or neutral monsters, why can't Ezreal's E do this?

Because he's already strong as he is.

Why doesn't his arcane shift stun on hit?

Because it adds strategy and options to his game play.

Because Ezreal (the designer) likes it that way and thinks it makes AP Ezreal (and AD to a lesser extent) harder to play, which is in his opinion a good thing, because he wanted Ez to be an all skillshots champ.

Skillshot implies chance to miss.

It should, especially for Ap Ezreal's sake (this skill is harder to land than his skill shots imo) but ad ezreal is just "too strong" and buffing him when he has such as high win rate would make no sense.

It never hits the wrong target if you don't miss with it.

ez is already too strong. god forbid we make him have to think about diving in on someone.

This will give him two skills that ignore minions. Harass much?