David Graeber is, as far as I can tell, a professor of anthropology. Which means he doesn't have domain expertise in any of the areas he's criticizing. Indeed, I could (flippantly, but honestly) say that I think "professor of anthropology" is a bullshit job, but then again I'm a severely left-brain guy and I'm going to assume there is a social value there that's just going over my head.
To put things another way: my wife once asked me what my interest was programming-wise. I told her it was compilers and programming languages. And she asked: well, don't they have those already? I strongly suspect if people get a 3% exposure to programming (e.g. writing yet another JS framework), like Graeber is doing with the various jobs he talks about, they'd think that programming is also full of "bullshit jobs." But that would be a conclusion arising out of ignorance.