Is a singer who doesn't write songs a "real" artist?

Here is a debate that has come up in a couple recent conversations. If you'd like to weigh in, here is the question: is a singer who doesn't write his/her own songs a "real" artist?

My position, which surprises some people due to my love for good songwriting and singer-songwriters like Dylan, Waits, Webb, etc. is that a singer is a musician whose voice is his instrument, and we should no more judge a singer who performs other writer's music than we judge a bass player for playing other writer's music. Indeed, the rise of the singer-songwriter and the death of the full-time writer has, on the whole, been bad for music.

Ex: The lead singer of a band has a great voice but doesn't write much, so people think of him as a lesser artist. Meanwhile, even if he WAS the band's writer, his bass player, drummer, lead guitarist, etc. wouldn't be judged badly for playing his songs rather than their own. They'd be judged by how well they could play bass, drums, or guitar.

Dylan, Lennon and McCartney made it acceptable, then cool, then a near-necessity for "real artists" to record their own material. Interviews with them, particularly Dylan, indicate that they themselves didn't intend for this and don't think it's a particularly good trend, because the truth is great singers who can also write great songs are rare. I've heard many great singers performing their own material, only to come away feeling, "Is that the best you could do? Really? You couldn't find better songs than that? Like, if you had an average or worse voice (ala Dylan) or we just read your lyrics on paper, would they really hold up as well as the work of someone whose talent was primarily as a writer?"

I've heard people argue that a singer has to express what is in his heart, which is why he should do his own material. Nonsense. Especially in this age of easy communication, a good writer can get with a singer, interview him/her, ask "What's in your heart? Hopes, dreams, fears, passions, quirks. What do you want to express? Do you want to challenge people? Comfort them?" and the like, then write based on that. Later they can go over the material with the singer and modify/revise together. In this way, the singer may actually learn to be a good writer.

So having said all that, is a singer who can't write songs, or who leans on experienced writers, not a real artist? Or less of an artist, compared to singer-songwriters who come up with all their own material? What are your thoughts?