What the heck, the universal job description of a PM is to genuinely understand the requirements of their product. I'm always baffled how such people stay in those roles without getting fired.
I wouldn't want that job, but I also don't currently know how to bring demonstrable evidence that they're incompetent, either
I have roughly the same opinion about UX folks, but they don't jam up my day to day nearly as much as PMs
Otherwise, it's a matter of time until the house of cards falls down and the company stagnates (sadly, the timescales are less of a house of cards, and more like a coal mine fire).