The original series didn't necessarily spend all that much time fleshing out the details or background of the conflict between the Empire and the Republic/rebels, but enough for it to work, also because it was still more or less original then. The prequel series had probably the most detail in that regard, and benefited from being a prequel series where the viewers already knew where things would ended up, but wanted to know how it came that far.
But in this trilogy, they're just handwaving the politics to the point of self-parody, where we're supposed to support the rebels just because the audience should always support rebels, and supposed to hate the First Order just because they like to copy Leni Riefenstahl and vaporized a supposedly important planet in TFA which the movie had spent exactly zero seconds setting up before that point (yes, kind of like the original trilogy, but back then it was original - plus, they had an iconic villain in Darth Vader). I was hoping for better in this movie - and instead, we get nothing but 'the evil empire chasing the rebels'. Except I guess for the one tiny bit of nuance when Benicio del Toro points out that immoral arms dealers are selling to both sides. Which, somehow, was enough to get my local newspaper's movie critic to express his admiration for the movie.
I can't agree on your last point - I do like Rey. She's more likeable than either Luke or Anakin in their respective trilogies, I'd say, that's not really the problem for me. Not that she couldn't use more character development.