I’m usually self-contained when it comes to this subject. “But”…

Keynes wrote that, after increasing technological efficiency, people would gradually work less and less until our biggest problem would be to fill up all the leisure time we had.

Was that before or after being jailed for vandalism? :^)

Okay, I’m half-joking, to highlight that Keynesian economy followed by the letter leads to the broken window fallacy. Now to be serious, give this a check:

What, then, constitutes the alienation of labor? // First, the fact that labor is external to the worker, i.e., it does not belong to his intrinsic nature; that in his work, therefore, he does not affirm himself but denies himself, does not feel content but unhappy, does not develop freely his physical and mental energy but mortifies his body and ruins his mind. The worker therefore only feels himself outside his work, and in his work feels outside himself. […]

That’s Marx, from 1844. A “bullshit job” is just a pop name for a job that alienates your labour from its output. A bullshit job has some output because otherwise it wouldn’t exist on first place, but the worker himself sees that output as non-existent, unnecessary, or meaningless.