Perin and Sirigu are not better than Donnarumma, never have and never will be, if you are basing it on a couple of goalkeeping errors this season then thats not a fair assessment. Like i said Donnarumma has a way higher ceiling than perin and is the closest thing I've seen to Buffon at his age.
There's a reason why perin is being signed as our number 2 and not number 1, because he's not even better than Woj, and a reason why Sirigu was ditched by psg and playing at torino, and a reason as to why Donnarumma is being courted by big clubs to be their number 1