This impression has been reinforced as I've been reviewing the prequel trilogy. As critical as some might be of it, one thing that should be said for it is that it explains how the Old Republic was toppled by the Sith, how Anakin Skywalker fell to the dark side of the Force, and just what the Clone Wars entailed. In that way, it expanded on what we knew of the Star Wars galaxy, even if we weren't sold on the love story or fulfilled by the digital effects.
Episode VII, on the other hand, leaves a lot of wondering to do. This also, of course, brings up many *SPOILERS!*
I know, of course, that Episode IV left some of these same questions to be answered. They didn't detract from my enjoyment of that film, however. I also know that many of these questions will be answered in the novelization of the movie, the visual guide to the film, its sequels, etc. Even so, they leave me not quite as satisfied as I might have been had these details been included in the film. That won't stop me from seeing it a few more times, however, because it is an exciting and engaging motion picture.