On the one side we have supply constraints on necessities. If there isn't enough good housing for everyone and we're not allowed to build more then people will have to work 40 hours so they can outbid other people on the good housing and not get stuck in the bad housing. We could solve this by building more good housing, but only if we actually do that.
On the other side it's a question of where the surplus goes. You have a company that makes billions of dollars -- far more than it needs to operate. What happens to the rest of the money? If the managers get to use it for empire building, you get bullshit jobs. That happens a lot.
Ideally we'd solve both, but even just one would be progress.
If you don't have to work 40 hours to afford necessities then you're not going to choose a 40 hour bullshit job. You're either going to choose a real job or a job with lower hours so that you can spend more of your time doing something you want to do, which might very well itself be a real job (i.e. starting your own business).
Whereas if we can figure out how to transfer more wealth away from organizations and into the hands of real people, that gets rid of bullshit jobs too, because most of them come from the principal-agent problem and the misalignment between managers and owners/taxpayers. Transferring the money to any person or entity without middle management would be a net improvement.
If people's basic needs were met, I think you'd see a lot of labor shift to work that is valuable, but currently not compensated for.
Also, you have to adjust constraints to deal with legacy systems: the Federal Reserve works to maximize employment through monetary policy. This is suboptimal, when work will expand to consume the time allowed for it [1]. You need to use a one way policy ratchet to ratchet down the hours per week worked as productivity has increased, otherwise workers will never see productivity gains and society will be stuck on the 40 hour labor work week forever.
The feasibility of this (in the US) is strongly dependent on health insurance not being tied to having a full-time job (often defined as just under 40 hours a week).
Plenty of employers have demonstrated that they can be organized to use mostly part-time labor, but their incentive to do this has been avoiding the obligation and expense of contributing to health insurance and other benefits, rather than giving employees a productivity dividend.