While he's certainly introduced some problematic champions into the game, he's also done good things as well. Warwick, for example, and I think that Thresh is not only a really fun support to play as, but I think I also heard that he played a big part in changing what supports could really be.
He's had issues, yes, but he's done good too.
ZOE IS HORRIBLE
Yup, pretty much me. But
can go die in a hole.
Yeah I think he has done some real good stuff. He's definitely pretty creative. In my mind the thing he is mostly guilty of is something Riot's whole design/balance section is guilty of.
Homogenizing champions and making generalists. They make these really strong and really fun champions, but they need to make sure they are playable to generate enough interest, so they provide coverage for their weaknesses. His champs are definitely fun and interesting, but maybe just a bit too much.
Like I'm not 100% convinced Warwick needed a move speed buff considering he has a engage ult, a Q that lets him stay on targets, and a multi target CC on top of his ult CC.
And like Yasuo is another good example to me (I know both of these champs are really only OP in solo Q, but you know). It's like a mobile assassin who also scales quite well. Just abuse the fact that he is melee in lane! Oh wait, he has a shield that regens like every 5 seconds in lane that will absorb about 90% of your harass damage until you maybe complete a couple items. Well abuse his range in fights then! Oh wait he has a windwall, so something like an Ashe being able to arrow him and go on him before he goes on her is not an option like it is with other melee assassins.
Thresh is probably the most well balanced of all his champs in my opinion. He's fairly well rounded, but definitely has some glaring weaknesses to exploit.
Honestly, prefer a lot more a CT champion rather other bland characters that were used to be released back at the time like Syndra, Diana and Elise.
Not saying they can't be strong ( actually some of these dominated a lot on LCS ) or they can't be likeable, but they did really not affect the game much. Just picking the examples one is a tiddy Veigar, one is a "yet-another-allin- assassin" and Elise is a Nidalee that can stun. I am talking about generic feeling, strategy and means of these champions.
Yasuo is a skirmisher/assassin with synergistic engages and projectile denial rather than being an upfront damage dealer like Yi or Fiora and gave insight how a champion can feel good while providing utility to a team ( stuff that was later repurposed with Fiora rework), Darius was the epythome of the juggernauts, Thresh fundamentally changed the way supports have to be thought of, Graves rework changed how to thing about marksmens and how to make their play pattern different than simply autoattacking and moving. Hell even Mordekaiser got an awesome low-cost rework and added a lot of novelty to the bot lane, even thought it could not perform well. Zoe is the one that feels still too weird to me, not because of her skillshot but rather because i am not fan of ultimates with short cooldowns.
Contrary to popular belief, we actually need anti fun characters/weapons/builds in any video game. CT makes some infuriating champions, but the sure are fun. They also fit their themes so well.
Same. Though I value having fun in League over anything else, as at the end of the day, its a video game.
His champions are fun and do have moments that make you feel like did something amazing,nobody is denying that,but they're one of the most un-fun champions to play.
You're playing a melee?
You're use projectiles?
You're a top laner with a weak early?
You're not a tank? 
homeless windbag weeb
used farming equipment
most infuriating "support" in the game.
how bout no?
i know i'm missing someone but too lazy to look up.
######i love my plant.
The part I love is they changed Nid because they thought her chucking spears and chunking people was unhealthy. Then they created Zoe, who can put you to sleep so you cant dodge her long range chunking OH and also she is even harder to kill than Nid was. Makes me smile.