why cant you stop ezreals ult?

every champ i name here i dont wanna talk about them needing buffs or nerfs its just examples.

so if ezreal (or lux, etc.) ults no matter what you do, if you dont kill him he uses his ult! you can TF gold card him, you can malzahar ult him, even tahm can eat him!!! he will finish his ult!

then there are champs like fiddle... he charges his ult... blitzcrank uses his r. fiddle is silenced and his ult stops and is on cooldown. why does this happen? how is this fair?

its even so unfair, when you have guardin angel and you "die" you still ult!!! ez ults, his hp hit 0 the moment he presses r, during the GA animation HE USES HIS ULT!!!

champs like fiddle malz kata are fucked! why is this happening? i dont get it.