Plato's "system" was oligarchy --an elaborate, gruesome, and explicit hierarchy of castes ruled by so-called philosophers. This political rubric reflected conditions in Athens with which he was intimately acquainted, being a paid informant of wealthy benefactors there. He was a selfservin sumbitch by measure. If you doubt, read his unanswered, Letters from exile toward the end of his life, during which his pupil Aristotle methodically finessed his social commentaries (Socratic "Dialogues") into a novel form of epistemology, generalized, "natural" history.
Republic. Read it. In its entirety, pls.

Diversity is the key to economic and political evolution.