“… what are we creating now that will still be valued and discussed hundreds or thousands of years from today?”
Well, there’s very little chance of memorable art to come into existence if artists are not paid fairly. Art takes time and effort, even for geniuses. If someone’s worried about becoming homeless or whatever, they’re not going to focus on their craft at the expense of health and safety, and even if they do what they produce will be suboptimal or unfocused.
So what’s the fair value of such things? I suppose there’s a number of ways to determine that, but it doesn’t matter if the platform that’s hosting an artist is not acting in good faith nor practicing fairness. Really, there should be an open source version of Spotify.