I dunno about preachy, I think it just hit the "oh shit we've actually got to find a way to end this", and instead of sitting down and working it out to put together an ending that made sense, they just threw together a bunch of stuff inspired by the creator's religious beliefs and some metaphysical mumbo jumbo and called it a day. Lazy and incoherent? Sure. But it never felt preachy.
That said, I think if you ignore the way they winged the main storyline for basically the last 2 seasons, a lot of the smaller arcs were still great and had a ton of emotional resonance. Like when they found Earth and it turned out to be a nuclear wasteland and the way everyone reacted to that (the scene where Apollo's wife killed herself was intense), watching them forced into working with one of the Cylons, watching the Cylons splinter as they tried to learn how to function as a society and failed, the Zarek/Gaiter mutiny, watching the Galactica fall apart, etc. Even the ending, although it made no sense from a narrative standpoint, was fairly touching emotionally, with Adama flying off with Roslin, Starbuck's disappearance, Tyrol bailing on humanity, etc.
Like I said, I'm a big Stargate fan, but it just didn't have anything like that. It was great for what it was, but they're on completely different levels.