I think Riot misses that in a balanced state, Yasuo should probably have a 40-43% win rate

They're buffing Yasuo, but realistically he's fine at the moment and if anything is overtuned.

Why is his win rate garbage? Because of who the champion is, what he does, and what players want him to do.

Yasuo is an melee AD carry champion, in fact the ONLY melee AD champion that can survive and do well in the ADC role (despite being perfectly viable in top/mid as well). That alone should tell you he's pretty strong.

More specifically though: Yasuo mains are dedicated to him, so they play him in ALL matchups, including the 90% of matchups that are WRONG for him. Yasuo IS A NICHE CHAMPION. Just because Riot's metrics show he gets played broadly and with a lot of experience, that doesn't change what the champion's kit is. He plays about half of his games in the mid lane as an AD damage dealer. You shouldn't be picking an AD damage dealer in to all AD teams (and yet Yasuo mains do, and they don't get punished enough for it because he still shreds through armor without a last whisper). He plays the other half of his matches in the top lane when the team has no engage or tank. You shouldn't be doing that either - most top lane players will pick something tanky or with engage when their jungle and support don't bring that to the table. Yasuo players pick Yasuo. So again, he should be losing the majority of those games because he doesn't bring anything to his team comp, and again Yasuo players aren't punished hard enough for that because he out-lanes most top lane champions and then scales better than them anyways.

Finally, in either position, Yasuo is built to depend on allies' knockups. He should be a niche champion that is picked in to a comp that has knockups to help him use his ultimate on multiple key targets. Yasuo players pick Yasuo in to teams with no knockups, and they don't get punished for it.

Yasuo is DESIGNED as a niche champion that should thrive in a composition with allied knockups, allied magic damage, and allied tankiness/engage. We're talking about him going with a Malphite top lane, or a J4 top/jungle, an Alistar support, etc...

It's no wonder that Yasuo doesn't thrive when the meta doesn't support those picks (outside of J4). A 0-damage top without a knockup does not help your AD mid.

If Yasuo players will play him in every matchup, his win rate should be low. So why are you buffing a champion because his playerbase plays him suboptimally? That's just going to make him WAY too strong when he's picked in the appropriate setting. Better to punish the players that pick him in the wrong teams, than to make him a free win for the ones that use him properly and make him a 50-50 otherwise....