226th Rule of Acquisition: Don't use deus ex machina
The Ferengi made the series interesting.Much praise has been heaped on the writers, deservedly so in some episodes.But ultimately the Federation was saved -- deus ex machina -- by annoying aliens loitering in a wormhole.Any writing teacher will tell you not to use deus ex machina, so I must ascribe the unsatisfying series ending either to laziness or lack of imagination, neither of which is desirable in a sci-fi series.