First of all, slavery is an advance over autarkic total war in the Hobbesian state of nature. A slave is better off under this system than outside the polis. He has personal and job security.
But such an economy, if it is to “work,” must be accompanied precisely by division of productive activities between tribes. (Division of labor comes later, under feudalism.) There is trading going on between the socialist family-states.
Modern socialism would envision a return to a slave society without any such division of productive activities between tribe governments / entrepreneurs. This is the essence of the socialist calculation problem. An attempt to establish global socialism must result either in perfect stagnation or, since this is not really a possibility, in economic chaos. There is no way for the central planner to calculate a way toward improvements of production based on new knowledge. Human progress under socialism is impossible.