I'm not convinced all the activities enumerated as "zero sum" are really zero sum. Justice is worth something, crimes would happen even if there weren't any polices so policing is also worth something.

However, looking past this weaker aspect of the argument, there is a lot that is worth talking about here. There can indeed be competing processes that are so optimized and near maximally productive that doing one process depletes the small amount of resources that would make the second process possible. The limit that technological progress pushes us towards is not that of people all going to manual one-to-one, face-to-face labor but of getting near the physical constraints of energy, space and matter. Pushing towards these limits means that everything starts competing for natural resources and energy.

We are starting to see very high competition for space in technologically advanced urban areas. Energy and raw materials have always been subject to competition. This is where the true "zero sum" game lies (until we colonize other planets I suppose).

To illustrate, imagine we lived in a world where labor was unimportant because machines did most things better than humans could. These machines would still required time and natural resources (space, energy and matter) to produce goods and services.

For most people, "working" in this world would consist of going online, buying or trading an amount of energy, buying raw materials or spent matter that is ready to be recycled and pressing a "Start" button. Machines would produce some new goods or services.

Some people may also work on designing new better machines that produce finer goods. This would be mostly creative work as the technical part would mostly be automated. The machines could be specialized for maximum efficiency and quality.

People wouldn't have to go out to work. Machine owners could watch webcam feeds of their machines working in an industrial park somewhere. The finished goods, spent matter (trash) and the machines themselves, would be picked up and delivered by self driving delivery robots.

To get some variety, people would trade the production of different machines and they would trade excess spent matter. They would also trade the machine designs and the land or space to host the machines. The machines would sometimes have to be replaced when worn out or obsolete.

Total energy production might be constrained globally to a more or less fixed rate based on what could reasonably be captured from the sun. Total production would be limited by this. People might own and trade shares of energy production capacity.

There could be a level of inequality in this society. This depends on how much governments would allow ownership of things to be concentrated, especially ownership of energy production. The key thing to combat inequality would be to not allow too concentrated ownership of energy, matter and land and also make sure everyone owns or have access to the robots that turn the raw materials into goods and services.

It is true that as we get closer to maximum efficiency, it becomes more and more difficult to raise productivity. We should start to think about how a society can run under these types of limitations.