No S?

A rank is judged by how well you did compared to other people who also use that champion, and Yasuo is the kind of champion that some people use so well, that it drives the difficulty of getting a rank up for everyone.

The best way to get an S is to either play a champ in roles that people don't usually use them in, or get really, really lucky and get every kill in the game and never die.

Would've been an easy S on like any other champion (maybe Jhin and Lee aside.) His playrate is so high that the sample of players you need to beat statistically is a bit higher up there.

At least I think that's how it works.

It also doesn't really help matters that this was your score after a 44 minute game.

I would imagine if you had something like this under 30 minutes you might have got an S.

I'm not saying you did poorly, but all this means is that others have done better.