"The slightly shady crew of a ramshackle spaceship try to keep flying, while staying one step ahead of the law . . . ."
Trust me, just about any plot can be boiled down to three paragraphs (or less) of back cover copy!
To be fair, though, I do remember arguing about Firefly
with a friend who kept demanding to know what the crew's "mission" was, as though he couldn't get invested in the show and its characters unless they were defending the galaxy or fighting to overthrow an evil empire or searching for the secret of the universe or whatever.
He needed it to be "about" more than just keeping body and soul together out on colorful frontier worlds.