I think, they were all dead at that stage (having died at different times but there is no time after you die kind of a thing) I think the "lives" they were living were things that they would have wanted to sort out in their actual lives. Like Jack having a son to act out his father issues, sawyer being a cop instead of a criminal etc etc.
I suppose the last episode in particular did lend itself to that especially with Jack saying he died and his dad saying it's ok that he was dead/died too.
The door leading to the clichéd white light made me think that they were still alive where usually I suppose the white light is presented as the gateway to those that have just died. Still, I enjoyed it overall - I didn't get the feeling you did of redundancy within seasons and whatnot. Perhaps I'm just a fanboi!