Quite the contrary. Yasuo literally thrusts his sword in a straight line. He doesn't take aim, he just thrusts and whatever is in it's path, gets hit. The analogy is spot on. Teemo blinds him. So what, he will just cut right in front of him and if the little shitter is there, he will feel the pain. Simple, easy to understand, it works. Just like irl a blind person will still hit someone who is right in his face, if he just cuts with a sword in front of his face, so will yasuo in game. It's the exact same thing. It's a skillshot, it's thrown in a straight line, hitting whatever happens to be there or nothing if nothing's there. There are no complications, no complex concepts.
You can't take Aim while blinded, that's why melee or ranged attacks that are targeted will fail to hit. But, shit thrown in a direction, not aimed at something, will hit whoever is in their path. That's how things work. And it works the same in game. If i am playing Caitlyn and teemo blinds me and stands still, Cait's AAs will miss because she had to aim them but her Q, which is just shot in a direction, will obviously hit you if you are there, why? Because it's a Skillshot.
If you want to make a change to how teemo's Q makes shit miss, you should only make Targetable/Aimed shit miss and the thing about that would be that, All point and click spells would miss, which, tbh, playing mostly skillshot oriented champions like Zed, i agree with, it makes sense, how will you aim that fireball as Annie if you're blind? Food for thought