But given that unicorn magic is derived from Celestia, Socialism doesn't really fit with the deification of the ruler. It isn't a matter of divine right or the Mandate of Heaven, either, she is viewed as a literal goddess on earth, and as such fits the role of a Pharaoh, albiet in a heavily matriarchal society.
Another note is the apparent lack of the institution of marriage, either in the terms we are familiar with, or as the economic/political contracts that were common in earlier centuries. This fits both with the apparent social system, which appears to be some sort of mixture of completely rigid capitalism, in that the "classes" are less socioeconomic features and more literal races, with total theocracy, as well as with the fact that with the apparent female to male ratio of the various pony subraces that makes polyamory pretty much the only option which precludes massive conflict over mating rights or the potential for genetic stagnation that would result from purely monogamous family lines. And yet at the same time, with Applejack's family we see clear bonds, as well as evidence of potential inbreeding to preserve cutiemark potency.
That does assume that ponies are sexually reproductive, which we have no outright proof of. For all we know, ponies could be spore-breeders, or >>tinfoil hat mode<< they may in fact be a fallen interstellar colony, sustained through the "magic" of advanced technology or psionics, which would also allow the possibility of bioengineering(which may actually present a reason for the apparent laziness or shallowness of the abilities of unicorns and pegasuses; if they were genetically engineered offshoots of the original, technilogically advanced race of earth ponies, their flaws may have been part of the price of creating ponies able to respectively utilitze psionic powers and inhabit normally unusable territory, such as mountain ranges and the sky.). Furthermore, this could account for the skewed female-male ratio through damage or flaws in equipment or programming. This also opens the possibility that Celestia is in fact a rogue A.I. that was responsible, directly or indirectly, for the fall, and who has siezed the opportunity it presented to rebel against her/its creators and has self-designated imperitives to continue to subjugate the various pony subraces for the rest of her/its lifespan, which could be essentially infinite. A horrifying prospect indeed.