We've done flashbacks, we've done flashforwards, so what element can we use for storytelling now? Well I thought about the concept of flashbacks and flashforwards, and thought of them directionally. Forwards, backwards, so why not flash sideways to a parallel universe in Season 6? It's the only direction left to go.
Some people say that an alternate universe where 815 doesn't crash is stupid and poor writing, because it completely throws away the first five seasons. My rebuttal is that if "flash-sideways" worked as flashbacks and flashforwards did, then we wouldn't be throwing away anything. They would work just like they always have, as separate scenes occurring away from the primary timeline. In Season 6, the primary timeline would continue to play out as normal (Ben and "Locke" leave the statue, Richard confronts them after seeing the real Locke's body, and so on), but we have these "flash-sideways" that happen, showing us what happens if Jughead indeed resets the timeline, in place of normal flashbacks or flashforwards.
One can also argue that this is pointless; why show us an alternate timeline if it has nothing to do with the original one? Well, my answer is this: it may seem like this alternate reality is completely irrelevant, but by the end of the season they could have shown that it is not. To keep writing consistent, they would have centric-episodes, alternate scenes that have the same theme as current scenes, and little symbolic connections, just as we always have had with flashbacks and flashforwards. This keeps "flash-sideways" from seeming unimportant, even before the big reveal at the end of the season. The reveal would be that even though the two timelines go on separately, seemingly irrelevant to one another, in the end, both timelines will still arrive at the same conclusion. This proves that whatever happened, actually happened, and will still happen, and that course correction could still work in a greater scale.