Worth to point out that there is a huge difference between people considering their jobs meaningless AND their job being meaningless, though.
(In general I think while plenty of people are familiar with varying levels of pointless effort in their jobs, it's rare that a whole job consists of that, at least as far as the person doing it and the person hiring for it are concerned)
I didn't read the book "Bullshit Jobs" [1] as an attempt to quantify how many jobs were bullshit. The author was an anthropologist with no interest in quantifying the economic impact. It's lots of amusing anecdotes from frustrated workers and a nudge for people to question the efficiency of capitalism.
At least that's how I read it. But reading the wikipedia page it sounds like a lot of people fixated on the idea that society could double its efficiency. Hard to know if there's a correct interpretation of the book's claims, and unfortunately we can't ask: the author David Graeber died in 2020.
Well, again, there is a huge difference between one's own perception of their job being useful or not. I believe garbage collectors, janitors, and nurses, are not examples of useless jobs. Useless jobs are mainly in the office, called "paper pushers". I mean come on, have you not been to any jobs (nor heard of any) where you had to pretend you were busy just to get paid? I saw plenty of cases.
I'm not sure how it's possible that anyone over the age of 30 can say something like this with a straight face. Have you ever worked anywhere? I'd love to know how the "researchers" have discredited this. I'd also love to see their other papers (likely, also, bullshit).