"Waaah! The Game is Unbalanced! Rito fix!"
https://www.youtube.com/watch?v=bsC8io4w1sY
Spend the next 8 minutes watching a video that discusses why game developers intentionally create unbalanced games before you about the overall game being unbalanced. (Hint, it's not some scam.)
Now, with that being said, are there problems with the game state?
Of course there are. Lethality is still a massive problem ever since Riot gave assassins two brand new items that pack it in the class rework. On top of that, tanks, specifically divers like Hecarim and Vi have become massive problems due to Courage of the Colossus and now take and deal as much damage as juggernauts while completely ignoring their primary weakness: immobility.
TL;DR: Yes, Yasuo is a cheese champion who has way more damage built into his kit than almost any other champion in the game, but that doesn't make him broken. Riven is still Riven due to her high skill cap. Ryze is continuing to one shot squishies with a QWQEQ combo.
All of these champion-specific details aside, though, doesn't make them broken. They're actually what makes the game fun.