Summary of why Quinn's rework feels bad
This is as simple as I could make it. Basically, I think that the new reworked version of Quinn shares many traits with old items/champions that were reworked becase they had fundamental issues.
- Quinn doesn't have power windows anymore.
Quinn is a bit like pre-rework Ryze, where she slowly scales up in damage (and exponentially thanks to her innate), but doesn't really have any windows of power/weaknesses. It's even more true now that getting a CS with Q soft-resets its cooldown. Another thing that makes it so is the fact that each Harrier proc is now weaker, and Harrier is available much more often. So basically, she no longer has power spikes and dips that both team can use, and she will either be oppressively strong by being consistently ahead, or uslessly weak by being consistently behind.
- Quinn relies a lot on invisible power.
Quinn is a bit like pre-rework Sona, where a lot of her power comes from intangible effects, or effects that passively helps her team. A lot of her trading power comes from attacking a Vulnerable target and gaining AS/MS. Additionally, she also relies on passive/tangential effects to thrive like vision and "outside of combat MS". Those are all powerful effects that do not feel very rewarding to use (a bit like an aura).
- Quinn limits a design space that she doesn't occupy.
Quinn is a bit like pre-rework Statikk Shiv (Ionic Spark), where she occupies a niche and thus prevents similar designs, but she occupies a niche part of that niche, meaning that she's not fulfulling the niche. Quinn is a roaming DPS champion. The problem is that you mix 2 roles which don't fit very well together (roaming and DPS; roaming is usually paired with initiators or assassins; whereas DPS is usually paired with sieging or poking). So this means that that "roaming specialist" design space is occupied by Quinn, but you can't realistically use Quinn for that role because she comes with additional restrictions.
- Quinn doesn't have a clearly identifiable personality.
Quinn is a bit like pre-rework Sion, where she has a lot of good abilities and cool concept, but they don't tie together very well. When you look at the champion, you can clearly identify a playstyle that has potential and everything, but no matter what yo udo with it, there's at least an ability that feels somewhat out of place, and it never really fits with what the champion looks like.
Please don't release a pre-rework Quinn to replace the current (somewhat unsatifactory) post-rework Quinn.