re: Firefly
The "universe" is largely inconsistent in Firefly, as I have seen references to "galactic" activities in official sources. I get the impression that the producers were uncomfortable in this territory and are basically avoiding the discussion.
The anime series "Cowboy Bebop" also assumed a spectacular level of terraforming of our own solar system in a very short time.
BTW, without star drive, how would the human race GET to this "moon filled solar system" in the first place?