That was basically my thought as well, but I still say it plays well as a stand-alone story to give someone a taste of Trek. They may be confused at the beginning of the episode but I feel it’s self contained and focused enough that most people can pick up the major beats from context (Cardassians = occupiers, Bajorans = formerly occupied). And then hopefully the acting, the mystery, and the twist ending are enough to, like you said, make the viewer want to learn more.