You know what would literally fix EVERYTHING about yasuo? This one simple change.
So you know how when Yasuo knocks up with his Q, they are considered "airborne" instead of simply knocked up? So for his ult, make it so he can only ult on AIRBORNE targets instead of any simple knockup. Obviously this ruins his ult somewhat so we would have to inc the damage probably, but this one change would make Yasuo actually have to do something to ult instead of just waiting for the smallest knockup (which could literally be a Trundle pillar pushing someone one unit to the right) to press the R key. It makes him reliant on his kit only.
: Knockup
: Airborne
: Atmospheric conditions are reading good. Lift off in 3...2...1!