Ive heard all the "reasons" before. I just don't understand them:
"Damage too much given his defensive kit"
Yasuo's dmg is not that high. It only looks high when he gets to fight other squishies. BUT I would argue that their damage (mages) in most cases is actually the same or higher, but is burst as opposed to sustain. Yasuo's damage is like that of any other raned adc- item dependent, but he has to be in melee range.
"defensive kit" he has a shield, and a windwall, but in spite of that still had (and probably still does) one of the highest average deaths per game as a champion. This isn't skewed much either between high and low elo. He is incredibly easy to kill.
"CC plus cc extend" The cc isn't easy to land on max range, and if he is using it point blank he is putting himself at risk being melee, unless he is fed, but that is every champion. His ult works on displacements, but also animation locks him for the duration he is extending the cc. This fact alone is one of the reasons he dies a lot, since teams tend to wreck him for using his ult.
"windwall makes it IMPOSSIBLE to trade with him" (emphasis added)- I understand the exaggerated tone here, but the statement is obviously just wrong. EVERY ranged champion has a full rotation of spells with a lower cd than windwall. Windwall is stationary and again, Yasuo is melee. If he puts it up, he either has to sit behind it- in which case you can back off, or he has to walk through it- unless you are going to also just stand on the side of the wall letting him stab you through it. and of course you could also simply move to the side and its useless vs melee matchups. Is it strong, somewhat... Situationally, its godlike. But not specifically in lane.
Honorable mentions:
"He is weak early, and you can shut him down, but once he gets PD he takes over the game"
This is obviously a claim that gets repeated and I have never seen this once happen. Show me ANY video where Yasuo goes 1/8 or 0/5 and is down a bunch of cs, then gets JUST Phantom Dancer and takes over the game with his SUPER HIGH DMG with ZERO bonus AD and 60% crit chance. Blows my mind. I watch a ton of Yasuo gameplay. Havent seen it yet.
"He is braindead easy to play/carry with"
- Said no High Elo player ever. No, his kit isn't super complicated, but making it work takes lots of practice and good decision making. One of the issues RIOT had with his kit is that its actually not rewarding enough for the players who master him- having one of the lowest winrate differences between his master players and his experienced ones.
and 
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I don't want to see any sort of buff to him maybe adjust his passive but otherwise don't give him any damn buff.
Here you go, did you hear anything about balance about this champions before ? Nah