why do people hate...

Because he's infuriating to play against? That's pretty much it.

Same way it's infuriating to play against Teemo as melee top. Yasuo's just a lot more frequently played.

Sure he may have counters but if you aren't playing a champion with one of those counters there is nothing you can do aside from being extremely more skilled than the yasuo. There really isn't middle ground for him.

He gets a lot for free. Mobility. Manaless. Free shield, Free double crit. Annoying to try to land any skill shot (since Riot is trying their damnest to remove any Point and Click CC). Mainly.

Has enough abilities for 2 champs and literally has something that can work against everyone.

When you vs yasou you have. Zero counterplay against him because of abusive mobility and ult cancelling bs

I dont know about other people, but ill tell you why I hate yasuo. So a couple of things first and this has nothing to do with the kit itself, but it is the fact that when people play him it turns into an either he gets super fed sort of thing and the game just ends, or he feeds so hard that he cant do anything (and those are the ones you remember) because they are on your team. Also the attitude that many yasuo players have is largely negative I dont know what it is about people who play yas, but the second they get ganked or they start stomping its all chat city with them. Just causes cancer one way or another.

Now for the problems I have with the kit itself ill make it short. Q is fine. W sucks to deal with if you have a ranged anything, E is top 3 least favorite abilities in the game the cooldown is too short and there are too many ways to use it, R is also ok. Oh also passive is also cancerous. So yea there you go.