I actually think a lot of Project Managers do a good job, and are valuable, but surprised nobody has mentioned David Graeber's Bullshit Jobs theory.

That is documented at https://en.wikipedia.org/wiki/Bullshit_Jobs and https://www.vox.com/2018/5/8/17308744/bullshit-jobs-book-dav....

It specifically mentions "taskmasters" who manage/create work for others, and project managers might be put into that category by some (but again, not by me as a general rule).