Well, it is quite possible that your family may be slaughtered by storm troopers beforehand which I would argue would nullify your obligation.
Yeah, maybe Lucas missed an opportunity for greater complexity there. Luke comes back and has to argue with Uncle Owen that his desire to leave is now not just his longstanding, primarily selfish desire to go to the academy, but represents a obligation to a larger community, the galaxy as a whole, that supersedes his obligation to the small community of the farm.
From the descriptions of Divergent that I've read here and elsewhere, it does seem targeted to a particular age group, young adolescents, who are just taking the first steps of self-definition. People at that stage of their development need to frame things as a manageable set of personality options, hence (what to an older mind is) the cartoonishness of a whole tribe committed to bravery, and a different whole tribe committed to intelligence. What do the brave people do all day? Do they brush their teeth more bravely than the intelligent clan does? But that's the way for the young mind to frame these things up as rankable priorities.
But then not-fitting-in-to-these-norms is valorized because 1) not fitting in is how young people feel, 2) not fitting in to old categories is the life-project they're engaged in and 3) the young mind half knows that the five-tribes breakdown is reductive and that no one fits in such monolithic categories.
Hollywood may or may not no how to make good sci-fi movies. This is a sci-fi movie in outward appearance only. It's a fable, and a mechanism for youngsters to mature. And Hollywood will make a lot of those, because that audience will pay money to define themselves by imaginatively aligning themselves with the Team Edward and Team Jacob du jour.
Star Wars was mine, and it had some of the same cartoonish reductiveness. Every planet, for instance, is an x-planet: desert planet, ice planet, jungle planet, city plant.