The problem with Lux still isn't the fact that she can kill you
It's the fact that she's got better harass than most mid champions on top of that amazing kill potential, and none of it has any long-term cost. You are supposed to commit to high risk to get high rewards, but Lux can play in an extremely low risk manner by throwing snares from 2k range until one hit and you die.
Not even mentioning her support tier utility combined with all that damage on the same kit, riot gutted support's damage
because of their utility, but
gets to keep both for some reason.