Artists don't generally try to OWN styles or prevent others from using them. They are the result of years of training, adapting, etc. They put their own spin on it. It's effectively a brand of that artist, and it's generally beholden to a sort of "honor" code that you'll likely get called out for breaching if you're flagrantly trying to pass it off as your own.

The core issue illustrating this is when people use an artist name in a prompt. If these models did not exist, if you wanted something in that style, you would likely be reaching out to that individual, or asking someone else to try to emulate someone. In that instance, the emulation is generally accountable. In these instances, there is no accountability towards the algorithm, as it's not making creative choices, to say nothing of moral or ethical ones. That was done by the individuals with venture-capital backing, using research loopholes to fund the legally questionable scraping of this data in the first place, which in some instances, violates the EULAs of the sites they were scraped from.

At the end of the day, these artists, styles, etc. would not exist without the artists who had no say in their "democratizing art".