This makes no sense. In ANH we are given a glimpse into the universe, yet nothing is really explained there either. We know there's a force, we know that Obi Wan was a Jedi and so was Luke's father. We hear of an Emperor, but never see him. IV was designed to be told as a story already happening, we are just jumping in at that starting point.
In TFA, we know the Republic is back. The First Order rose from the ashes of the Empire. Luke was attempting to rebuild the Jedi Order and was betrayed by an apprentice. Snoke uses the dark side of the Force and got to young Ben early and seduced him to lead the Knights of Ren. All of this is explained in the film.
Rey was left behind on Jakku for a reason, that will most likely get a lot of development in VIII. How was it not a competent film? TFA was re-establishing us into the universe 30 years after the fall of the Empire. Its a world building film (and somewhat getting the train back on the tracks) and was written as such to be part love letter to the fans of the OT, and part world-building to establish VIII and IX.