That seems awfully harsh. I mean, most people are average kinda definitionally. :)
I’ve seen two issues in this area. The first is simple mismatch of expectations. It’s actually fine if you expect PMs to do UX, as long as you hire PMs who are good at UX and then visual designers. The problem arises when you hire designers for their UX chops and then expect them to accept PM-driven UX—especially if you don’t hire PMs with UX expertise. You’ve basically just set up everyone for failure. But the reality is that the definitions for designer and PM are really inconsistent.
The other potential issue is inconsistent leveling. A lot of companies value the triad of PM, eng, and design, but level the designer at least one or two steps more junior than the other two, putting her at a disadvantage. As the first designer in the door at Heap, I pushed hard to be at the same level of reporting structure as our VP Product—not because I’d mind reporting to him, he’s terrific—but because it sets us up to keep that leveling even as we grow.