I think Yasuo is very good in Soloq, because if you are good at using this champion you can carry the game and win obviously.

I think it depends on the league where you are, because if you are in low leagues (Bronze, Silver, Gold), you can pick Yasuo in any composition, because you can destroy the players with this champion even not having a knock up (like the ult of Gragas, the ult of Malphite, etc.)

But if you are in the other leagues (Platinum, Diamond, Mater and Challenger), you can only pick Yasuo if the composition of your team have a knock up. The reason of these is because the players of this leagues know that you are going to throw your tornado, and they are going to stop you before you do that. But if you have a knock up is more easy to activate your ultimate and kill everyone.

Is very important to practice with Yasuo against bots, because if you don't practice you will be destroyed in a game with normal people. The only trick with Yasuo is to practice and practice. One day you can become a good Yasuo and carry the game.

One of the ways to learn how to play with Yasuo is watch people that know play Yasuo. These people are streamers that play yasuo very good.

I personally recommend:

Bjergsen: https://www.twitch.tv/tsm_bjergsen
Darshan (ZionSpartan): https://www.twitch.tv/zionspartan