I got pretty torn up by this episode, and it had a lot of poetic stuff. The "awakenings" in the sideways were a sweet and well done way of revisiting and saying good bye to all those Losties we came to love. I really liked the ending with the plane taking off and Jack's eye closing, even though it was a mirror image that we couldn't help but see coming. I think they must have used shots of mirrors about 108 times in season six.

In "The End", Jack lived together, and he didn't have to die alone. Kate, Sawyer, Claire, Miles, Richard and good ol' Frank Lapidus all survived and escaped the Island forever. Hurley and Ben stayed behind to become the new Jacob and Richard - but with their own set of rules, dude. I guess Desmond stays with them too? I suppose that was his sacrifice. Rose and Bernard will live out their days in an Island paradise. And at the end, almost every other character in all of Lost was dead. (Uh, Walt? Aaron? Oh, nevermind!)
But we all die sometime, and most of the Losties met up in the Island's waiting room, in a Unitarian church, so they could all go together to their next stage of existence.
The root of it all, was that Jacob needed someone to kill his brother. Because of the rules that were established by Mother, Jacob is not supposed to hurt him. And because Jacob turned him into a smoke monster, the Man in Black was incredibly powerful and resistant to most damage. The only solution would be to shut down the magic of the Island, turn MiB back into a mortal, and then kill him.
Apparently, for over 2000 years Jacob recruited people to the Island trying to find his candidates, and who knows how many lives he altered. For instance, he might have manipulated the Shephard family for generations, who knows? In 1867 Magnus Hanso crashed on the Island, and in the 1970s his great-grandson returned to build the Hatches, seeking to stave off the end of humanity. Coincidence, or fate? Hard to say.
But what DHARMA never figured out, nor the Others (because Jacob never told anyone but the final candidates) was that the true danger was from his brother, the Monster. The Man in Black wants off the Island, and Jacob believes his escape could threaten the existence of everyone in the world. We'll never know if that's true, or just what Mother told him. In the end, it's possible that everyone lived and died because of a sibling rivalry that had no other consequence on the rest of the world.

Anyway, just as the Man in Black had a plan to kill Jacob, his brother had a plan to get his revenge. And Jacob's master plan involved an assassin and a fail safe, as well as a replacement. By pulling the plug on the Island's source of power, Jacob could turn his brother back into a mortal but the Island would sink. So, like something out of one of those point-and-click adventure games, he had to assemble his team and his tools. Jacob's candidate would learn how to kill the Man in Black - once the water was drained.

Whoever went in there at the end was doomed, so Desmond was there to take the first plunge into the water and pull the plug. Then, Jack battled and killed the Monster, and returned to the Source. Before he went to face his destiny, Jack anointed the new Island protector: Hurley. Then, he put the plug back in and fell into the pool, saving the Island and maybe all of existence.
The Source is protected, the Monster is destroyed, and the world goes on turning.
It's not quite the end of the story though. Some power granted the Losties a reward for their struggle.

There are dozens of ways to look at this. It's so vague, any viewer can come to their own conclusions. It's sort of a masterpiece of vagary. Here are some of the ways I like to look at the ending of Lost.
The Time Loop/Nirvana Theory: these characters have been born, struggled, and died, many times before. Each time, they battled against evil incarnate, and each time evil destroyed the universe, snuffing out all life. Then the cycle starts again. This time, Jacob finally managed to line up the proper candidates to defeat his brother. Then, the cycle started over again anyway. That's the sideways. It wasn't until each of the key candidates could "Let go" that they were able to stop the wheel of life, and move into the light together. They basically achieve Nirvana, and never have to be born again into struggle. Ben, Mrs. Widmore, Ana Lucia and the rest who we saw were "not ready" will have to go through another cycle, and hope they learn the lessons of the Island
We All Join Together: Throughout each individual's life, every person we meet makes an impact on us. Some people are truly special to us, and there are certain moments in life that make up the core of who we are. Those bonds are bigger than life, and tie us to the spirits of everyone who was special in our lives. When we pass on, we're united with a part of each of their spirits. And a part of us goes to bond with each person we knew, in their own special "sideways".
Island Reward Theory of Purgatory: The Island holds the power to eternal life. It creates a reality that's a holding area for all the souls who pass over it. Those who are "ready" move into a golden paradise together. Those who are not get to stay in the sideways. This is their reward (or consolation prize) for being pulled into the struggle to defend the light.
We could go on and on with this. The Island could be a living creature, somewhere between X-Factor's Ship and a Cylon Raider. It crashed on Earth a long time ago, and the original protector was an alien. Humans have been recruited to defend the ship, and a few were granted unnaturally long lives by some alien technology. Other technology onboard inspired human civilization, or leaps in technology like the Industrial Revolution. I mean, take it wherever you'd like to go with it. The producers left it astonishingly wide open.

At the end, Lost was never really anymore than what was presented at the beginning. A group of characters with "issues" all struggling to find redemption. It was generally about life and death, fate and free will, faith vs. science and all those other things. But in such broad strokes and sweeping generalizations, the writers completely failed to take a stand or say anything meaningful about any of it. "It's all about the journey, man."
I spent a lot of time writing about Lost, theorizing and trying to draw conclusions from the mess of a story. Even right up until the end, I thought I might be writing about it for a while. Picking apart little details as I tried to make sense of the whole story. But overall, Lost is so vague, so wide open, I'm not sure it will reward further viewing. I hope that with a little time, I'll be drawn back to the stories and characters I loved so much for all those years.
But in the end, it all seems empty. Each season was it's own little play, with new characters, plots, sets, and the rest - all swept under the rug because they kept writing themselves into corners. A series of repeated actions, images, and themes that add up to nothing but repetition for the sake of keeping things going. (Although, a lot of those images were pretty cool)

All through season six of Lost, I've been watching old episodes of Star Trek: The Next Generation which is full of stories about time travel, alternate "pocket" universes, situations where something is "not quite right" and the characters must follow clues that lead them back to their "real" lives. All season I've been saying "Oooh, Lost could end with something like that!" And now when I watch an episode, I think, "Ohhh, Lost could have ended with something like that!"
For instance, I watched the episode "Clues" which more than ever reminded me of Lost. After the cold open, the characters are all unconscious on the ship. They wake, and it seems only thirty seconds have passed, but small details: an experiment that kept running, a clock that's out of synch, a transporter trace - all point to a period of "missing time".
The intrepid crew of the Enterprise gets right on the case. Everyone shares data, and they quickly assemble an outline of the events. They figure out there was an alien intervention, and Picard gets this great speech:
"The plan failed because clues were left behind that suggested a mystery. (there were) little pieces of evidence that suggested even more clues. And to many humans, a mystery is irresistible. It must be solved..."
It's great, watch it:
Ohhh, if only Lost had ended with something like that.
Clearly, the characters of Lost are not like the characters on Star Trek. No one on Lost seemed particularly curious, or interested, or helpful. For the most part, they weren't very likable. In the end, the producers told us that the mysteries we all found so irresistible were actually irrelevant. "It's all about the journey, man."
I feel like it was a bait and switch. I hoped for a group like the crew of the Enterprise. In season five the producers said they were going to "let our geek flag fly" when they introduced time travel. I hoped we were heading toward an ending more like that episode of Star Trek - the characters we love striving to make sense of things, and learn what it's all about. Instead, it feels like a generic multi-faith cop out that failed to address the majority of the story they had built up.
I feel so incredibly disappointed. Maybe one day I'll feel different. I don't know. But, I once set out to make the stupidest, mysterious short film I could think of, with a twist ending that was so dumb it invalidated the entire story, yet almost made sense.
Guess what I chose as my ending:

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