In "The End," Jack had planned to hold the funeral services for his father in Eloise's church. After Desmond helped many characters to remember their lives on the Island, they all met at the the sideways church. In a chapel filled with symbols of major religions, Jack found his father's empty coffin, just as he did on the Island. He then met his father, who helped him to understand the nature of his reality: Jack, Christian, and all of the people in the church had either died before Jack or a long time after him, but they and their lives were all real.
Now they were ready to "move on" and discover what was next. Jack entered the nave of the church, where he found Kate, Sawyer, Juliet, Hugo, Libby, Desmond, Penny, Jin, Sun, Claire, Charlie, Aaron, Sayid, Shannon, Boone, Rose, Bernard, and Locke. After they all had greeted each other warmly, they sat in the pews. Christian walked to the back of the church and opened the doors, revealing a bright light which filled the church as everyone smiled and we assume "moved on."
Who arranged this after life meeting? It appears that Christian was the master of ceremonies since everyone was waiting for Jack to arrive. Arrive in the sense of "awakening" memories of the Island. It was Christian who told Jack the muddy answer to the series great mysteries:
1. People in the church died before or long after Jack.
2. But "they" and "their lives" were "all real." Meaning that the sideways world realm was also real as well as the Island world.
3. That "they" created the sideways world as a place to wait for his arrival.
4. That there was no "time" in the sideways realm, but merely "now."
5. And once together, they all could "move on."
6. The church guests were the most important people in their lives.
This does not explain if the characters created the sideways world (as a holding room in the after life) would not remember the Island/real world prior to their own deaths. If the sideways world had no function of time, then there was no need for a complex alternative reality of Jack married to Juliet, having a child, healing Locke, etc. The souls would merely need to be in sleep mode until they all arrived at the church. And this is where the Answer falls a part; if everything we saw was "real," then it was all by series definition, "unreal." If the dream/fantasy experiences the characters created in the sideways world are "real," then the same could be said of the Island experiences. Which leads to a big sinkhole question: if both realities are real, then how did the 20 characters in the church find themselves, bind themselves together, to journey to the after life?
And to be perfectly honest, not all the characters got along on the Island. Example, Rose and Bernard were fed up with the lot and went off on their own. Locke and Jack never saw eye to eye. Sayid turned into an evil zombie. Jack and Sawyer were at odds most of the time.
Also, there were no deep, strong, global character connections prior to Flight 815 crash on the Island with the 20 friends in the church finale:
Christian: Jack's father
Jack: knew Christian; chance meeting with Desmond at stadium
Kate: knew no one prior to the 815 flight
Sawyer: knew no one prior to the 815 flight
Juliet: knew no one prior to the 815 crash
Hugo: may have known Libby at the mental hospital
Libby: may have known Hugo at the mental hospital
Desmond: knew Penny; chance meeting with Jack at stadium
Penny: knew only Desmond
Jin: married to Sun
Sun: married to Jin
Claire: was pregnant with Aaron
Charlie: knew no one prior to 815 flight
Aaron: knew no one prior to being born on Island
Sayid: knew no one prior to the 815 flight
Shannon: knew brother Boone
Boone: knew sister Shannon
Rose : married to Bernard
Bernard: married to Rose
Locke: knew no one prior to the 815 flight; but maybe aware of Hugo working at box plant.
Besides limited family relationships, there were no strong friendships or bonds between the entire group of characters and each other prior to the 815 flight. But we are told by TPTB that it was all about this group in the end.
The conclusion was not about the plane crash, the Island, the smoke monster, the hatch, DHARMA, the Others, Widmore or the freighter, Rousseau's science team, rescue or return, time travel, Jacob, or MIB. We were told that it was about the 20 people in the church who had the greatest impact on each other during their collective lives.
For those who loved the LOST ending, this character "feel good" reunion was enough. The statement that the show "was all about the characters" is only true to a certain point. A story teller needs to move the characters through events in order to reveal truths to the audience.
Now, for some who don't want to acknowledge the issues with Season 6 and the End, they claim that the brilliance of the series is that the creators left the questions unanswered so the viewers themselves could fill in their own blanks. That is a cop-out. One does not buy a mystery novel to read and then find the final two chapters missing. No, critics say there should have been a viable explanation at the conclusion of the series. Why were those 20 people in the church so important to each other to the exclusion of their other family members or pre-flight friends?
A year after the finale, the LOST phenomena has all but passed into the footnotes of television history. Some consider it one of the top ten shows of all time. Others ponder the great first seasons as a missed opportunity for greatness in the disappointing end. A few truly believe that the series should have concluded at the end of LOST's fifth season - - - with a real cliffhanger instead of a headscratcher.