The laws of shemitta alter the definition of the decision-making agent.
Whereas during the six years of productivity the decision-making agent was the self-interested individual or firm, during the shemitta years that agent becomes the community. It is not that the community becomes the agent for the decision-making over the individual but that the individual seems himself as behaving according to the tastes and preferences of the community. By altering the laws of property with respect to the elementary needs to sustain life while at the same time foreclosing the producers of those needs from working for the market, the members of the society could attend to matters driven by higher spiritual concerns.
If spirituality is grounded in materiality, there comes a moment when the materiality has to flip around and serve the spirituality, and that moment is shemitta. Shemitta alters the axiomatic presumptions of the economic system. It takes the initial endowments of, on the one hand, material goods, and, on the other hand, tastes and preferences with respect to those goods, and it says let's change the game once every seven years and another once every fifty years. During the years of shemitta and yovel your endowments are not your own and your tastes and preferences are driven with respect to what you can make and not what you can consume.
Every shemitta year people behave as if they won the lottery. Shemitta makes the entire society behave as if abundance and not scarcity were driving all the economic decisions.