Divergent the movie - lessons for writers

So I took my daughter to see Divergent at the movies.
You may have already read why I think dystopia is a much better genre for teenage girls to be reading than vampire fluff and I can say, having read the book and watched the movie, nothing has changed my mind there!
This is not a movie review by the way, although it will contain some spoilers ... rather it's a case of how I felt the movie-makers fell into a couple of classic writing traps.
Discussing the movie versus the book with my daughter, it got me thinking about how easy it would have been to take the movie to the next level.
The movie was pretty good and in fact I think handled some aspects of the story better than the book.
For instance, the battle to capture the flag was a great deal more intense and exciting than the book. Likewise the sequences where Tris has to get through her fear simulations in front of the Dauntless leadership made much more sense in the movie. In the book, she does display Divergent tendencies in her simulations - which would surely see her dragged off and killed, about 2 books too early. The way the movie handles it makes much more sense.
But where the movie falls down is its emphasis on external action over internal action. It may be that a Director's Cut of Divergent comes out, which will fix those issues. But the cinematic edition was flawed.
Take, for instance, Al's suicide. In the book, Tris is rightly devastated because, when Al was at his lowest, when he was struggling to come to terms with fighting and hurting other people, she rejected his advances. She blames herself.
None of that made it into the film, so you don't feel the same towards Al's death. After all, he tried to kill her - why does he deserve our sympathy?
Likewise when she is forced to kill a mind-controlled Will. In the book, Will's friendship has helped her survive training and protected her when Peter and his cronies were after her. Plus he is in love with her best friend Christina. Little of that makes it into the film, so you find yourself saying to her - shoot him! He's going to shoot you otherwise! Yet in the book you feel her anguish at being forced into this situation.
The emotional angle, which gives so much more meaning to the action, has been stripped out of the movie.
And that is a classic trap for writers - particularly writers of spec fiction. Never discount the emotional angle and remember that action should have an effect on characters' relationships, as well as everything else. It just makes the effect on the reader all the more powerful.