Don't like cheating? Then cheat too!
With logic like that, this game wouldn't need a balance team OR a punishment system. You could just do the same things every other scumbag is doing.
Also you've already highlighted yourself why it ISN'T fair. There are over 100 champions and league, and roughly 30 have this bug? That leaves over 70% of champions at a MASSIVE strategic disadvantage just because of this bug alone, and more specifically the hordes of mimicking troglodytes abusing it. That's a pretty damn broken gamestate.
Additionally, maybe I don't WANT to play those 30 champs. Maybe I wanna play someone I actually like playing because of their intended kit and playstyle, and don't want to have to narrow my champion pool down to one based exclusively on who can abuse a massive unintended bug in the game. Yours is exactly the kind of mentality game designers struggle to prevent from cropping up.