Stephen Saito “I Love You Forever” has all the trappings of a romantic comedy, for better or worse. In the whipsmart millennial-skewing film where you’re old if you’ve been caught using a third-generation iPhone, there’s something charmingly antiquated about the scene filmmakers Cazzie David and Elsa Kalani set around Mackenzie (Sofia Black D’Elia), a law student who has a pair of bickering best friends (Jon Rudnitsky and Cazzie David) to constantly amuse her and a personal life punctuated by Jessica Simpson and Michelle Branch needle drops.