Two things about the characters. First, they are meant to be ambiguous, so that we don't know who's a hero or villain. Legends about the artistic richness of ambiguity notwithstanding, ambiguity doesn't communicate. Ergo, the characters are left undefined.
Second, they tend to be dividing up between ordinary and special. Jason Ritter in particular is supposed to be ordinary. And Laura Innes in particular is supposed to be special. Ritter is convincing as a real person but lots of people don't want to see real people on screen, they want larger than life figures who may not be realistic but are at least entertaining. Personally I find the more realistic one more interesting. However, for those who do prefer larger than life, the special one, Laura Innes foremost, are still not compelling because they're just cliches.
The flashbacks are so a long backstory can be compressed into a short time, and so character development can be highlighted (as in bumbly boyfriend turns hijacker!) and so they can recycle the same scenes. I think every action scene was showed at least three times.
As to the twist, it reminded me so much of an episode of Miracles I don't think it was accidental.
As for other shows, the flashbacks have nothing to do with Lost's soap opera approach. The sketchily implicit politics have nothing to do with 24. The 4400 varied wildly in quality, from godawful to pretty good, but it's serialized story never had any resolution nor did it ever intend any, so far as I can tell. It was willfully arbitrary in its plotting, bordering on fraud. And, last, Brannon Braga's name in the credits notwithstanding, FlashForward's pilot was much more exciting.