Ok, let me try to understand. Han Solo is a more substantial character because of his history as a smuggler, the Millenium Falcon, and Chewbacca, right?
Finn is a stormtrooper who defected. Let that sink in.
The above statement has repercussions throughout the film, and is a subject previously never even considered in the previous storylines. A stormtrooper was usually a mindless soldier who couldn't hit the side of a barn with an RPG. Here, they become living, breathing souls with minds of their own.
Yes, a lot of the scenes were similar, and I don't think that was a mistake. JJ Abrams set up the film as both homage to the earlier ones, and as a bridge to an infinite future. The final scene alone has implications that could span the next few decades of Star Wars fans. There are so many questions left to be answered, so many plot lines to explore, and a literal universe of possibilities.
I didn't grow up watching Star Wars. My friends and I binge-watched the entire series in the nights before the premiere, and TFA feels like a natural progression of things. I have no clue what kind of character development is to be expected in the events occurring in the few days the movie took place, but what I saw was enough to convince me that it's more than worth following. Especially if they keep up the awesome cinematography and action scenes.
