Seeing as you used Fred Durst as an example of a good metal signer, I am not sure if I can take this seriously lol.
It is the same with most genres, you have your good signers and your bad signers. Ke$ha is terrible and Fred Durst is terrible. Such is life. The proposition that metal is designed for bad signers is false, for you can find bad signers in any genre, and there exist death metal vocalists with beautiful vocal capabilities - such as Mikael Akerfeldt.
For a better response, metal as a genre does not necessarily have or need so much reliance on the vocals as other genres however, as more emphasis is placed on the instruments. In other terms, whereas a different genre may have the instruments as mere accomplices that help accompany the vocalist - or harmoinze to make the signing more memorable -, a metal group puts equal emphasis on all instruments - depending on the subgenre of course. This is one reason why in metal we have "bands" (like Opeth) where in other genres the artist will go by a singular title like Lady Gaga (despite the fact they have instrumental accompaniment, the emphasis is on the vocalist).
TLDR: That's equivalent to the statement that Pop music is best designed as a platform for bad instrumentalists. In reality, this is not true as we can find great musicians and vocalists in all genres. What you are instead doing is comparing different genres - and more specifically subgenres - based upon norms that can be found within that genre that may not reflect upon all practising musicians as a whole.
#1 Amb-ass-ador
