The essay lays out a wide range of reasons why normal people reasonably fear that their OWN lives are going to get worse, but your assumption is that what they really care about is the lives of artists, despite the fact that you admit that they understand they have always lived in a world where nearly all artists get very little back compared to their efforts?

That seems more likely your own sentiments, rather than an plausible explanation as to why most people have feelings on this issue.

I'm not saying that this isn't the main reason for some people (for example artists fearful about the technology) or that it doesn't come up in conversation in some niches--young educated people from the West who are terminally online.

But is it really likely to be a true root cause of broad concern across society?

No, they don't care about the lives of individual artists. They care about art, passion, creativity and the interplay of these with human culture. They also care about growing inequality, and they fear potential loss of their careers, both financially and in terms of the meaning it gives their lives.