In my experience, western fanartists always had a very unappealing artstyle compared to the japanese, over years and years, only a small minority raised to the top in quality.

Nowadays AI can produce on-model, non cringeworthy, and very appealing artwork of western characters, which fulfills a content gap.

Now, western artists could make a fuss and scream about how much they deserve the business, but if their art sucked to begin with, they werent going to get the business in the first place.
I think theyre complaining less about AI, and more about the fact that people have an alternative to whatever sub par thing theyre providing is.

This notion that anything you make has inherent value is meaningless, a person can make a sculpture of shit, just because a human made it, doesnt mean anything. doesnt make it special. （ ´,_ゝ`）

Likewise, a robot could make something so appealing it resonates with the viewer in the same way human made art might. Doesnt matter where it comes from, what matters is its appeal to the viewer.
Also, if anyone has ever used a local AI model you would find that its actually a skill in itself to make something look "good" and people can spend hours upon hours adjusting node structures or prompts to make something decent.