This show felt like the writers didn't really know what the story was going to be about when they started airing it. It was almost like they threw each episode out there and then waited for feedback from a focus group to decide what they were going to do next. I'm sorry, but simply writing a story that is about "a mystery" isn't enough.
By the end, the show was getting better, but I'm sure it was too late to salvage the ratings it was receiving.
Apparently, it's much harder than it looks to spin a yarn about unanswered questions and keep it going for multiple seasons, as Twin Peaks, X-Files, and Lost managed to do.