So back in the day--"the day" in question being 1900-1960ish--vocal stylists would perform the works of Berlin and Gershwin and Rodgers and Hart and countless other composers. This was the standard--slight pun intended. It was part of jazz, musical theatre, and pop music.
So how did we come to scorn any singer who doesn't write their own music? An accomplished pianist can be lauded for rocking out Bach and Chopin without ever writing anything of his own. It seems that the voice is the only instrument that has quite suddenly become packaged with an obligation to create as well as articulate. It hardly seems fair.
The same people who might look down on a pop star for having a limited hand in the composition of their work is the same person who might revere Nina Simone or Ella Fitzgerald. These women aren't famous for their compositions. They are famous for their voices.
So when did singing cease to be a talent and an art? I mean, throughout the ages it's been so that anyone who wasn't tone deaf could sing. In the 20th century with an increase in mass communication, radio, television etc, personalities came forward that elevated vocal phrasing to an art form, past the operatic. It amazes me how artists can be decried for a lack of originality when the vast majority of popular music and entertainment is founded on a bed of covers, remakes, retellings and reworkings.
It just seems intentionally snobbish to disregard the work of one in favor of another so arbitrarily. I will not give specific examples as I'm sure anyone with firing synapses can make their own comparisons. I suppose I'm just continuing my ever present quest for perspective. One band is inspired by another band: awesome. Johnny Cash covers some classic songs and it's art, but someone covers a Johnny Cash song and it's blasphemy? It don't work that way.
Originality is in articulation. It's not the song, it's how Judy Garland sings it. It's reorchestration, it's reimagining. Musical Theatre is not rife with "original" work. In the Heights is an original telling of a fairly standard story. In the words of Stephen Sondheim: Anything you do, let it come from you, then it will be new.
How hard is that to accept? If it doesn't work for you, tis well. But let me tell you that while you may lament Britney Spears covering "Satisfaction" someone was saying the same thing about The Rolling Stones, back in the proverbial day.