It's impossible that there is simply nothing in the world that needs doing.
Exactly how to make sure that things that need doing, are done, is what economics and politics are about, but any "job shortage" is because of inefficiencies along some spectrum, not actually ever a natural state.
The word "job" as used here is a technical term. It doesn't mean "anything that needs doing". It doesn't mean "anything I find enjoyable or worthwhile". It actually means "activities that someone will pay me money to do because I can do it better, faster, or cheaper than anyone or anything else, including machines." (For the purpose of this discussion there's also an implied meaning of "someone will pay me enough money for those activities that I can purchase adequate food, shelter, and discretionary items so as to have a reasonably comfortable existence.") That set of activities appears to have peaked in per-capita terms and is probably on a decline which will accelerate rapidly in the future.
So yeah, you're right that this problem is inherently an economic problem, not an "I don't know what to do with all my free time" problem. That doesn't make the problem any less urgent or less difficult to solve. It's actually incredibly difficult to solve because it'll involve rejiggering our social contracts, which will probably take several generations to complete.
