Classical musicians and ballerinas alike spend their lives and careers paying tribute to the great artistry of long-dead composers from highly-regarded eras of classical music, from baroque to romantic. There's enough material there to fill several lifetimes of study and performance. It's a perfectly valid form of challenging yourself, bringing out new details in old music, and keeping said old music alive.
This isn't comparable to some producers selling their songs to a company and the company going, "Okay, here, Group #11, take this," repeated ad nauseam. It's not a cultural movement, it's not honoring anyone or the past, and while some songs might be challenging to adapt to, you don't spend years studying for it.
It's true that none of these artists write their own music... but the similarities end there.