Plenty of authors of space opera make political statements with their stories. They often give definitive answers about how various political systems will turn out.
- Tolkien: benevolent monarchies and agrarian collectives will win out over corrupt dictatorships. (Okay, not Space Opera, but still relevant because Vulcans are Space Elves.)
- Star Trek: Secular “humanist” federal star empires will win out over feudal monarchies, provincial federations, totalitarian collectives, and theocracies. In the Alternate Universe, totalitarian feudal dictatorships win.
- Star Wars: Militaristic empires will be forever locked in power struggles with revolutionary federations of all the other sorts of governments.
- Honorverse: constitutional feudal democratic monarchies will win out over corrupt socialist empires.