The sheviit/shemitta system addresses the maturation process an economy goes through to become an ecology. It speaks to how the political and the monetary systems work to shape the economic system.
It addresses the relation between surplus and class struggle. It says the problem of surplus and class struggle can be dealt with through a careful shaping of the laws of property.
The key is to use the laws of property to define the line between satiation and excess, not only the line between standards and practices and satiation.