"Everyone has something to offer."

Sorry, but that's nonsense. I'm all for not erecting unhelpful hierarchies, but is there no difference between (searches for non-contentious example, fails) Linda Thompson and someone whose voice is so poor they couldn't carry a tune in a bucket ?

That isn't, before the accusations fly, to say that only certain kind of voices work - one of my favourite singers in Chavela Vargas and she hardly possesses a squeaky-clean X-Factor voice.