I agree that Reborn is simply a more poetic word than rebuilt. Seriously do not get why it is so hard for people to just accept the simplest explanation; that we merely went 5 years into the future as stated. Not an alternate reality, or the distant past. If you look at the trees in the new shroud, the tops have all been sheared, and the growth obviously new. Most of the new buildings are wooden, and easily built in less than 5 years. It has been stated that new ruins and areas have been uncovered by the devastation of the Dalamud event.

Land recovers pretty quickly from natural disasters in the real world. I sincerely doubt that anything we have been shown is beyond reason in 5 years, especially when magic exists to aid it. I just don't see a need to conjure overly complicated explanations.