I think Yasuo is a very interesting case in that I don't find him particularly broken, and he doesnt have anything in his kit that could be seen to be as toxic as Fizz's playful trickster (maybe windwall, but I find that easier to play around), yet he gets a lot of hate relative to his winrate and playrate.
I think this is a result of Yasuo being too well designed. This may sound weird but hear me out. Yasuo is a very fun, unique, and satisfying champion to play. Everything in his kit can be used in a non-linear way, so he has a very adaptable style, he has variable build paths (although the semi-tank one is definitely more popular right now I'd say), and he also has different playstyles in that he is capable of solo-carrying and split pushing, but he also packs a lot of utility and can be played primarily as a teamfighter. He also encourages people to keep playing him as he has a kit that rewards familiarity more than most (kind of like Lee Sin or Vayne in that his skill cap inspires people to main him).
So what's the problem? Well, the result is that although Yas has a very fun and unique kit, it has a TON of stuff packed into it. Yasuo is the definition of a champ with an overloaded kit. Having windwall as a basic ability is evidence enough of this. The problem is that when facing a Yasuo, if feels that he has way too much at his disposal to outplay you. So even when you die to Yas and you're like "wow I got outplayed" it's not really that satisfying because it just feels like he had 100 tools at his disposal while you only had a couple. So instead of saying "this yasuo is clearly better than me" it feels more like "this champion is clearly better than mine."
So in my opinion, even when Yasuo isn't broken according to the numbers, it still can be a frustrating experience to play against him, and champs that are frustrating to play against are the ones that get the most hate, not necessarily the most broken ones.