All markets must be perfectly competitive (whereas most of ours are not); if such a world existed, the requirement of perfect competition would rule out any division of labor or long-run economic growth.
There must be an infinite number of futures markets?— one for every good in existence, delivered at every future date, for the rest of time. And yet, in the model, time doesn’t really exist: all economic decisions for all of human history were made in an auction at the beginning of the world.
Moreover, far from being harmonious, this theoretical world has been discovered to be chaotic?— perpetually in random motion, never actually arriving at any of its “optimal” configurations except by accident. This finding alone nullifies the very meaning of the theory.