I think many missed the point by John

As I read through these comments, I think many people didn't follow the show as closely as they think, or understood the show for what it was, and/or missed many answers throughout the series. The flash sideways, which is limbo and not purgatory, was needed due to the was the show kept referencing death throughout many episodes. Some of these comments were direct and some were in a more indirect approach. Some ideas that I think many viewers missed out on which were brought up many times throughout the series.

1. "Live together, die alone." According to Jacob, they were all flawed like him in the sense that they were all alone. Not only until they were at the island they found friendship, love, etc. Even when the Oceanic 6 were back in the real world, they all drifted apart and were once again all alone. Even in the afterlife, they were still lost until they found each other again.

2. "What's done is done," and "Whatever happened, happened." This lies in the theme that the past is the past and you can't change what you've done in your life. Jack referenced this when he told Kate that he didn't care what she did before she got to the island. Ben also referenced this to Locke when he told him that he had to kill his father so he could let go of his past.

3. Fate versus free will. In tying with the above theme, you are either fated to your life because of your past or you can decide to choose to change the path you live (redemption).

4. Science versus Faith. In keeping with the above themes, science can't change events that happened in the past but your faith in people to become better people can do what science can't. I guess this is what disappointed some. In the end faith won out in the series as Jack gave into it. It's very clever what the writers did with the ending here because those that wanted a explanation of everything are fated to disappointment as the characters would have been if they had dwelled in the past looking for answers as the characters had been doing, but those who concentrated on the faith aspect would feel enlightened or fulfilled such as the characters since they had faith in each other and didn't care for answers about their pasts.