Michael Emerson, who played Ben in the series, is the only cast member who is still willing to discuss LOST. In a recent interview, Emerson said he liked and understood the ending to the series.
He explained that the series was not written in a linear fashion. He said that the various story lines were moving out from the center. (It would be like rays of light coming off the sun's surface).
Emerson said because of story structure and its emphasis on the characters, he was okay with how the show ended in "a spiritual way."
It is interesting to note that Emerson connected the ending as a spiritual conclusion to the show. The theme of science v. faith was the basis for the Locke and Jack leadership dynamic. It was when Jack abandoned his logical, scientific analysis of the situation to just going with the Island's flow when he became guardian, he found what Locke had seen. He found some form of internal peace.
But the sideways world was anything spiritual. It had the same elements of crime, passion, murder and lies as the Island realm. The final sideways church scene had no prayers, no reflections, no confessions, or no religious affirmation. It just showed a bunch of smiling people looking forward into the camera as the white light engulfed them.
And for those left behind in the sideways realm, like Ben, there was very little spirituality controlling their lives. Ben had tried and failed with his high school coup. He was in a dead end job. He was carrying the burden of care giving his disabled father. Was this his punishment? Or was the start of the relationship with Rousseau (through Alex) that would give Ben lasting inner peace? But that would be hard to imagine, since if Rousseau or Alex "remembered" the island world, they would remember how unkind, cruel and insane Ben was to them (caused them pain, suffering, and led to their deaths). How could either Rousseau or Alex forgive Ben for his island sins toward them?
A reasonable person could not forgive Ben. One has to live with one's decisions. Actions have consequences.
For if Ben would get a spiritual "get out of jail free" card with Alex and Rousseau, then why did Locke end his existence with nobody. He did less to harm Helen than Ben did to Alex and Rousseau. But Locke left the sideways world alone, without his soul mate.
Part of the "spiritual" conclusion to the LOST saga was a writer's trick to wrap up the diverse character story lines into a concentrated bundle of joy and reunion. But the basis for such a reunion is inconsistent and weak rationally based upon the story elements of the previous five seasons.
If it was truly a spiritual ending, then one would have to base the island world as the characters "living hell," the journey through the underworld of tests, tricks, pain, punishment, redemption and judgment. But certain characters got a pass even under those requirements, including Ben, whose only agony was his loss of the leadership role in the Others. He was not punished for killing anyone, including Jacob.
So the spiritual explanation to the conclusion of LOST is a valid observation, the underlying rationale for such an explanation is hollow.