Once that happens, of course the "black market" data aggregators won't care, but they're small and their product can't be used by legitimate channels so it can't compete in the mainstream market of ideas. What capital will do to screw over artists though is... Pay them. Once a framework is in place, a hundred or a thousand legit artists can produce enough AI seed-feed to legally supplant the work of hundreds of thousands.
This is the thing that will never happen, because all artists are interested parties, and as I said, they are not a unified bloc. So whatever solution big companies come up with for themselves, we all know ahead of time that they will 1) overwhelmingly benefit big corporations and 2) but insufficient to address artist concerns. When they coalesce around whatever standards they end up with, artists will still largely be making the same complaints.
If artists don't want their work to impact the world, they're free to keep it to themselves.
This whole discussion that we should allow individual artists to opt out of AI art through contracts or some other legal vehicle is a non starter, because it'll be impossible to administrate and enforce at scale, and there's too much incentive and ability for big tech to just ignore them and steamroll artists. They aren't a unified bloc, and even if they were how would they ever compete against big tech?
So what to do? Looking at productivity gains over the decades, it's not clear why we are still working as hard as we are. It's long overdue that productivity gains should come back to the people. Maybe "artist" shouldn't be a job title associated with profit/income seeking. If you want to be an artist, maybe society can support that.
Maybe instead of using all those productivity gains to do more more more, we can just work less for the same. Because it seems to me the more we work, the more they get richer. What if instead, they didn't get so rich, and we gave that money to artists in the form of grants, like we do for scientists. You do some art, apply for some grants, and you get some money to do more art. It'll all be public domain, anyone can use it, and big business gets to make a profit on it just like with scientific advancements (I have issues about that, but at least there's precedent).