How many of those unemployed people want to get a job filling potholes, or mowing the lawn at the park? How many are qualified to do anything about pollution in whatever specific sense you mean? What job does your average unemployed person get to "fight housing shortages" or whatever you're trying to say?
> What kind of system has work to be done but not enough jobs
Any system that isn't designed from the outside? Any system that's goal is not simply maximizing employment? Surely you can imagine a scenario with two civilizations, one has 99% employment, one has 80% employment, but the people in the 99% employed society are, on average, worse off?
> As long as we're choosing to make work about making someone else wealthy rather than satisfying all our needs
Most people would not say the number of potholes they encounter or the level of park maintenance is so poor that their needs aren't being met.
You take care of my needs I'll fill potholes. Plenty of folks would.
I haven't done the math, but my guess is that a pothole might do hundreds of dollars worth of damage over its lifetime, maybe thousands. If society was willing to pay 1/10th of that sum per pothole to anyone willing to fill it, there'd be a lot more applicants. (Though it might lead to people making potholes on purpose, so the payment needs to depend on road health over time, not number of potholes filled.)