Richard Bridge's comment is interesting.
"He never could sing, so how could he ever have a song? Call it a groan, or a rasp, or a grunt. "
I'm not having a go, but it seems that you are saying that a song can only be a song if the vocal technique lies withing a very narrow range of what you feel to be singing.
I'm interested to know where you would draw the line. Pavarotti would be OK I presume?
How about Sinatra, or Sam Cooke or Otis Redding?
And what about to distinctly un-classical Copper Family or Watersons?
Tell me, when you are under stress or feeling despair, does it not show in your voice?
Should you sound the same when you sing "Vincero, Vincero, Vincero !" as when you sing "I would rather go blind, Girl, Than to see you walk away from me"?
Should the emotion of a lyric not be expressed in the vocal tone of the singer?
Personally I find nothing more out-of-context that Conservertoire- trained singers doing Pop or Blues- and I don't think Rod would make much of a job of "The Magic Flute" or "Lohengrin" either.
However I do think that your simple, unsupported statement, Richard, is an example of narrowness. I see the same in some of my Steel Guitar playing associates.
-"I didn't like it. There's no Steel Guitar".
-"It's Mozart's Requiem!"
Cheers
Dave