Simple reason to why yasuo can't be viable

I disagree. Now, he is an assassin, and like all assassins if he lacks power, he lacks a hell of a lot. But 1.) He can extend knockups in an aoe while dealing damage 2.) He can Block projectiles for his team mates 3.) He is quite mobile, and while his base damages won't carry games, he can put them out quite frequently 4.) He has a fairly long range, if rather slow and situational, multi target knockup 5.) Has a natural shield that takes some of the edge off of poke harass and general team fight damage

He's by no means incredible when behind, but he has features he can make use of. It's just a matter of if his team was relying on him getting huge right away, or if they can carry through on their own power with just a little help

I think he's good, I just think people have unrealistic expectations of him when he's behind and haven't gotten good at locking him down and killing him quickly when he's ahead. Even just snaring him, if it's for more than 3-4 seconds, he'll die. He might take someone with him if he isn't stopped from autoing, but he'll die. It's not much different from Yi, his moves are just different so being good against Yi only gets you part way to being good against Yasuo. The rest is just getting familiar with the execution of it.

Totally agree. In game he is one extreme or the other, not much middle ground at all. Put him in a team comp with knockups and good luck beating him no matter what you pick.