Yasuo does not cover his weaknesses 100%. What he does is cover it more so than other champs.
Yasuo is not the only one to do this. A lot of other champs cover their weaknesses more than Yasuo, through other means.
The way Yasuo covers his weaknesses is with skill. Graves or Lucian, for example, cover their weaknesses with itemization.
if yasuo had no weaknesses he would have got 100% win rate already
yasuo is not immortal, yasuo's weaknesses is that he deals no damage before ult as he needs armor pen and his ult needs a knock up, and his knock up is not certain
additionally, his mobility is limited to a 400 range 10-6 sec dash that can be stopped by ccs unlike other dashes, until he has a lot of minions
windwall has a long cd
First of all, that's...4 weaknesses? Not a lot.
No he does a lot of dmg even without ult, excluding the fact that his ult has a relatively short cooldown. His lvl 2 is one of the strongest in game. He does not need armor pen early game. Lategame, he becomes more drain tank and less bursty, and, isn't as polar as he is early. This is an itemization based cover-up
his ult needs a knock up, and his knock up is not certain
This is a weakness that's based on skill, basically. Yas, however, gets the initiative with his E+q. If he only did his third Q, it would be 100% a skillmatchup. That is not the case, and, if it were, Yas would be bad.
additionally, his mobility is limited to a 400 range 10-6 sec dash that can be stopped by ccs unlike other dashes, until he has a lot of minions
How many top laners even have dashes at all. The ability for a top laner to even have mobility gives them much more outplay potential, rewarding them for skill more than immobile top laners. By having that dash, Yas has more windows to trade, engage, or escape than a immobile top laner.
Yas will dash around, while traditional top laners will be brick walls. How the dash is used is entirely based on the player, and is a skill-based weakness.
You will get the cocky Yasuos that you will destroy. You will get the god Yasuos that you will never be able to hit with your abilities no matter how hard you try, because of the gap in skill ceiling between your champ and Yasuo.
windwall has a long cd
It's based on how the player uses it. If the player misuses it by using too frequently, that's up to the player.
Windwall isn't as useful in top lane vs mid lane. That's a weakness for Yasuo.
There are many other weaknesses for Yasuo that weren't mentioned here though.