Diamond player here. I've played like... 1 game of Yasuo, and it was on PBE before he was released.
I guarantee I could go into a Bronze ranked game as him and utterly stomp the enemy team singlehandedly.
You being that skill level is a problem when you are playing that champion. I'm not saying that to be mean. You just don't have the mechanics, decisionmaking, zone control, etc. to play to his strengths and cover his weaknesses. Even if you know how to play the champion itself, you don't have the fundamental skills to succeed with a champion like that over a 30-40 minute game. But your skills (in those things) might be better than the average player at your elo since you are climbing with other champs like WK and Kennen. So stick with them.
There's a reason everyone says don't play Yasuo/Lee Sin etc. in Bronze. It doesn't matter how good you think you are with the champion. You can't play to their high skill ceiling because you aren't even close to it. And without being high in that skill ceiling, the champion is bad.