I will never understand why some champions get to stay toxic, while others dont

This title may be misleading but let me elaborate. Some champions are toxic, think lb, she got the nerf hammer for being too much of a bully, despite having some counterplay. Her ability to bully was considered toxic gameplay, and got nerfed. Ekko, however receives a free "oops i made a mistake" re-do button while also being able to be a bully to many champions. As another example, i believe xin has been strong since before sated devourer. In this time, i cant recall a time where he was considered "bad". He is very linear, very snow ball-y. In my opinion he is a little bit overpowered, and now thanks to bork buffs (thanks riot, rip any non ad champion again) he can easily do tons of damage with little counterplay, other than, you guessed it "cc". But cc counters everything so that point is highly irrelevant. Yi does the same shit. There are champions out there, like taliyah, syndra, lissandra, urgot, etc. that can be good and even useful sometimes, but can never snowball as hard, never can carry a game as hard, and when somehow, SOMEHOW, are good for the moment and make it in pro play, NERF HAMMER ( )