For those of us who weren’t alive in the 60s, the assassination of John F. Kennedy was a very, very, very bad thing for the United States of America, and for the entire world. So bad, in fact, that Peter Landesman took upon himself the task of dedicating an hour and a half’s worth of narrative solely to convey that exact idea. The result of his blunt-force artistry is Parkland, a movie that bursts with promise on the page but never manages to fully live up to its latent potential on the screen; branding the film a total failure would be dishonest, but so too would calling it anything above…