That's not all that related to sustainability. Sure, it might mean musicians make less but that's just supply and demand and supply is HUGE (still not infinite).
When you're in a constrained format like radio or cable tv you can only play one thing for your audience at a time. Because of that it's critical that what you play has mass appeal so that lots of people will be okay listening to it.
When you're in an unconstrained model that lets users pick what to watch or listen to, that mass appeal factor becomes much less important.
Sure, there's a HUGE array of music available, and each of us can claim that we think most of it's shitty. But when you actually start comparing what you consider shitty to what I consider shitty, I'd be willing to bet there are a LOT of areas that don't overlap.
This is the power that comes with being able to stream the content that the user wants. Mass appeal becomes much less important.
So yeah, there's a huge amount of music out there that I think is shitty. But there's an equally huge number of people that all have different opinions on what the shit actually is.
I'm not sure I understand your argument. I agree that in an unconstrained format mass appeal is much less important. Yet I don't feel some sort of 'good music' saturation point has been reached within the single subgenres (and subsubgenres) and I think that it will take a while for that to happen.
