Well, i don’t have a problem with the end of LOST. The OUAT writers though have consistently forgotten major plot points. It is possible that they will remember the undoing thing, but that would be one in a million for them. They have consistently forgotten things that have happened in the episode right before the one they are airing which is a pretty impressive lack of organization and just general care for the story. There is absolutely no coherence of story or character on OUAT, in my opinion. It is just a random occurrence of events with characters who behave differently based on random plot points and macguffins and deus ex machinas that jump in to save the day or mess it up.
It is just going to random its way out and then end.