I thinks it's wrong to think of jobs as way to bring a concrete benefit to other persons. The overwhelming majority of jobs exist to bring value to a company. And whether we like it or not, companies are the best way we found to produce technological advances.
In this way I don't understand your premise that a job is "bullshit" because you cannot describe it in 3 words. Good luck designing and mass producing the phone you're using to type this message with jobs we can fully describe in 3 words.
Now, If we were to imagine a perfect society where we use technology to relieve us from working, then yeah we could drop half the job for sure. But not the "bullshit" ones, the "real" jobs ! Cause we don't need cashiers and farmers is we use technology to replace it. But you still need an integration success manager to check that your OS works in all places it's deployed.
Yes, ok, I have a bullshit job.