You know why Rito went so batshit crazy with assassin rework?

Because they could.

No, seriously. They could do so, because assassin don't have any unique niche.

All assassins do is killing carries. Breaking news: Everyone can kill carries. Whole point of being a carry is that you die to a sneeze.

Would Riot do something like that to any other class, change it in it's very core risking it being weak as a whole, delicate balance of the game is ruined.

You ruin mages? Suddenly some games end in 15 minutes because there is no one to waveclear and drag when enemies snowball.

You ruin tanks? Suddenly all that's playable are skirmishers and fighters, because there is no one left to act as frontline for carries.

You ruin assassins, and suddenly marksmen are running rampant? Oh wait, they don't, they are weaker than ever. Because you don't need an assassin to deal with them - anyone can do this. From Nunu to Urgot, vast majority of champions has ways to dispose enemy carries.

Rito went crazy on assassins, because they could. Unlike with other classes, they can experiment on them for as long as they like, until they find good spot for them.

Because the game, as a whole, doesn't need them. Like it or not, assassins only point of existence is being fun to play for some people. Balance-wise they could not be there, so Riot can play with them until they find a solution they like - notice how last preaseason they were also heavily experimenting on armor penetration.