As far as I'm concerned, they did change the story. Juliet blew up a bomb on the Island under the premise that the plane won't crash and their future selfs would be alive. Well it's funny that, that is exactly how season Six started. Juliet says it worked and then we see 815 landing at LAX (opps, was that the Title or something ?) with everyone on it. Sure had me fooled. I was enjoying seeing how their lives were IF the plane DIDN't crash. Now it is just a " Good " show. Ending was okay for what it was, but it could have been Great !
Well It was misdirection but not a change in the story. Since season 3 we have been told that you can not change what happened. So I think that it is fitting that they couldn't change their lives with the H-bomb (It also explains what the incident was). If they had changed their lives with the H-bomb then what we had been told during the series would have been a lie. For me, what happened made more sense for the overall story.