He is far from alone in thinking that. Even among music critics that are generally positive about U2 there has always been a fair amount of criticism of his voice.
Ironic nickname, then ("Bono Vox" being the original form)
TIL what that actually means (the wiki bit below). Its also the name of a hearing aid company in Ireland [0], making it even more ironic. Pretty sure this is where the name originated from.
Found out that (according to wikipedia)[1]:
"is an alteration of bonavox, a Latin word which translates to "good voice"."