What's wrong with that? I guess I don't see the problem with having a twitch in jungle if it works, who cares if he's usually an adc? Making the jungle harder is just going to cement the very strong junglers that we have now as the only ones that can jungle.
The problem I see with having Twitch jungle is that lots of junglers have invested portions of their kit in being good at jungling. If you can just take an ADC or a mage and go do it, then those junglers will never be competitive, because they've invested power in something that's essentially worthless.
It's kind of the opposite (or maybe the contrapositive) of the top lane problem. If you dn't ever need something in your kit, then every champion who has that in their kit is just not good.
Making the jungle harder is just going to cement the very strong junglers that we have now as the only ones that can jungle.
I don't think so, because the very strong junglers right now are the ones with very strong ganking, not very strong clears. Lee Sin isn't the strongest jungle clearer, he's one of the strongest gankers. If clearing matters more, he's less good.