It wasn’t the overall concept of human extermination that was depressing; after all that gets threatened in most series. It was every single detail, every conversation, every facial expression in the whole series that just ground you down. It’s like the director and cast washed down valium with vodka before filming each episode.
Yes I hear you, It was described as a dark version of the original Battlestar Galactica series. A lot of it I just found ridiculous, however. The “Final 5” should have been called the “Original 5”, but the name was a plot device for the show. And how could it be impossible to tell Cylons from humans? Their spines lit up while having sex.