Many jobs are quite helpful and even necessary, if done for ~2 hours a day. They become "useless" in aggregate when they're forced to be minded by the same person for 8 hours (because of opportunity cost, effects on health well-being, etc., you end up "breaking even" or worse on QoL and net productivity).

Overall economic productivity is high enough that a lot of positions could be split into 2 or 3 short shifts, at full pay - IF you don't factor in the various financial boondoggles that we've gotten ourselves wrapped up in. If you made the decision to wipe out a lot of these obligations (mostly to rich people), we could get to that kind of set-up, solvently.