How can we tone down Yasous strengths that are not talked about or even noticed?

He is annoying to play because of his shield, range, wind wall.

But all of that is relatively OK to play around

However, what is almost impossible to avoid is his free farming anti-handicap and the speed of which he can reach you. A Dash costing nothing except for a specific circumstance but with way more benefits all while giving him another sort of auto reset for farming This honestly makes Yasou's farming extremely easy because he can farm while trading blows , the use of minions for mobility and q stacks are necessary for his kit but gives him unnecessary strengths in farming where his kit is not focused around. In the end, you just end up losing most trades because farming is a byproduct of his fighting play-style and you'll have abysmal farm because he can engage you whilst farming at the same time.

Then you might say" But you can counter-pick him!" that is 100% true ;However, not for the entire game. There comes a point where you must babysit yasou from doing anything and that starts in early game and never ends. If you do not annoying the living daylights out of him he will just obliterate you because he decided to farm the jungle instead. So winning against him in lane is only the first step to a long and tedious list of chores. He will roam, he will farm, he will breath. If you don't stop him he will just face-roll your team because you didn't pay any attention to him which seems rather unfair that you must give him 100% attention while he has to pay you almost none in return. If he shuts your down you have much less ability to recover (depending on your champion of course).

So whats a decent way to nerf him without even changing his abilities and dashes and such?

We remove the damage on minions(Not Monsters) from his E . If we remove this he can no longer rely on his second "sort of Auto-reset" for farming since he basically already has one. He can engage us but not longer farm as well while fighting this as well will help the person who he is against because a dead minion can't get aggro'd by yasou while a living minion can making engages need a lot more thought than simply Slide in with E, Poke, Slide back out with no aggro because minions are dead on the way forward and then back. This will hit his clear speed of course but it should be alot more fair for both sides if yasou is closer to the level of the enemies clear speed. This way he cant just face roll all over the map with some extra unnecessary damage that boosts his clear speed. So whats this other method that I also mentioned near the beginning?

While more unfair towards yasou I'm sure it can be fine tuned.The speed of yasou's dash should be lowered quite bit while its static cool down should stay at .4 seconds at all levels But to compensate for the slower dash speed each rank of the ability should add 0.75% to his max flow for a maximum of 10% So in the end it will end up like this

Sweeping Blade RANGE: 475 STATIC COOLDOWN: 0.4 On-Target Cooldown: 10 / 9 / 8 / 7 / 6 Sweeping Blade

Active: Yasuo dashes a fixed distance in the direction of the target enemy, dealing magic damage to non-jungle creeps and marking them briefly. The speed of the dash scales with Yasuo's bonus movement speed generate. Dash also gives ~7%/7.75%/8.5%/9.25%/10% of Yasuo's maximum flow innately as Flow-generation is based on distance traveled.

「 Magic Damage: 70 / 90 / 110 / 130 / 150 」 (+ 60% AP)

Each cast increases the next dash's base damage by 25% for 5 seconds, up to 50% bonus damage.

「 Bonus Damage: 17.5 / 22.5 / 27.5 / 32.5 / 37.5 」

Yasuo cannot use Sweeping Blade on a marked enemy.

While i'm sure this wont help with everything against yasou but it should make him at least sorta bearable