This was a documentary on ballet dancers in Russia that I streamed off of Netflix.
It was interesting to hear one of the girls talk about how there are no new ballets. I don't know how true that is, but I guess I do have a perception of "classical arts" like ballet, opera, and to a limited degree, orchestral music, being very reliant on much older works. Although perhaps a lot of that moved to musical theatre?
I guess the answer will be more obvious fifty or a hundred years from now, when things that are new now will have more historical weight to them. We'll see then if people are still staging revivals of Twyla Tharp and Andrew Llyod Webber.