I would like to invite other people to list champions that they feel carry hard in solo Q but are not used on the pro stage.
For me, why do we not see Master Yi 
? Sona 
? Udyr 
? or my favorite support, Fiddlesticks 
?
All 4 have massive effects on their games in solo Q. What makes them unusable on the pro strage?
So for yi its simply this.
Master yi dashes straight into an enemy team with his Q. This could put him at a bad spot considering he's not super tanky, he can also get locked down super easily if the players know what they're doing, and this is pro play we're talking about
Sona isn't played because she's too squishy and the only thing super good for a team fight is her ult
Udyr can get kited for eternity by all ADC's because they know how to kite, He's also useless in team fights
And Fiddlesticks isn't super great for team fights until 6, and the same goes with ganking, plus he also pops like a balloon and since fiddle ult is designed to initiate a fight if he ults he'll probably die instantly.
Yi and Udyr have a big impact by farming through a poor early game in the jungle but can easily be disrupted and set back by coordinated counter-jungling, something that's 10x harder to pull off in SoloQ. Similarly, Sona is a champion who doesn't have a big impact in the early game to pay off with a bunch of easy teamwide stats and a solid ult at 6.
Fiddlesticks can also easily get destroyed with some early counter jungling, benefits on poor warding to start his ult from a safe bush, and also likes when the enemy doesn't coordinate their cc to stop his ult before he can afford a zhonya's.
They all have a weakness that solo Q teams can't exploit nearly as well as the pros.
The Sona death ball can be monstrous if it gets going. But she's way too easy to pick off early game for the pros and she's a manna hog.
Fid was played frequently by pros for a couple of months. But nerfs relegated him again. Fid's real problem is he is frail and though he has a pretty good in, it's a channel, and he really doesn't have an out. And unlike solo Q, where 3/4 of the players think the only person that has to ward is support, the pros ward ward ward ward ward, negating Fid coming in from the flank by surprise. So you have to pretty much ult zonya's. But once you zonya, you're stationary.
Udyr doesn't really have an in either. He can run in. But Olaf does that better.
