I don't think his assertion is true at all. AI art can be quite good. I asked ChatGPT to make a painting that looks like it should be in a museum and the output was damn good. I couldn't find anything that would tip me off like I can with some AI writing. No idea how something like that would be embarrassing to look at.

And music. There are youtube channels for AI house music playlists that sound pretty damn good.

I guess if you're a high level art critic you might be able to easily see that some of this stuff is not good.