The BSG finale was…. not really overwhelming and not really underwhelming either. It was medium whelming. It gave an OK sort of resolution to the characters as a whole that’s moderately satisfying as long as you don’t think about it at all.
But if you do think about it….
The promise that the cylons “have a plan” was dropped from the title screens at some point, but it was definitely there early on and they really didn’t have a plan, or understandable motivations at all. They are one dimensional villains apparently driven purely by spite. Other things that weren’t really explained were: the opera house, which seems to have been an extremely complicated allegory to help Hera walk a few metres down a corridor, Starbuck’s resurrection and disappearance, and Hera in general.
Hera was supposed to be special. She was so special we had to endure two ridiculous plotlines to ensure she was the only part-cylon child after the writers accidentally introduced two other part or fully cylon children. The first being Tyrol’s son actually turning out to be a product of the least believable affair in the history of TV, and the second being Six’s pregnancy and miscarriage (peak soap opera). And in the end, Hera turned out to be special because… she becomes mitochondrial Eve. Literally any of the women in the fleet or on the planet could have become mitochondrial Eve!
And then at the end they decided to abandon all technology (including medical technology), because… ??? And everyone’s perfectly happy with that, despite having mutinied only a few episodes ago for far less.
Another special moment: When Adama is picking a replacement admiral to stand in for him while he’s gone, he says “We need someone the fleet admires and respects… so we’re picking this guy who occasionally stands in the background! Well done, extra, you’ve earned it”.
I mean, I enjoyed the series as a whole, even though it went downhill after half way through S2, but you do have to switch your brain off for a lot of the later episodes. Which is frustrating as it was intellectually intriguing to begin with.
I think a good example of doing this stuff well is Life on Mars and Ashes to Ashes. They managed to keep the intrigue right until the end, and then it concluded in probably the only way that really made sense, but was still unpredictable.