“Only the Brave” is the latest in a string of reality-based disaster films in which horrible tragedies are brought back to life via special effects and offered up for the delectation of the multiplex crowds a sub-genre that has become so prevalent as of late that Mark Wahlberg has pretty much made a personal cottage industry out of them. This is a type of filmmaking I have always felt a certain level of ambivalence towards because good intentions can’t hide their tendency to feel hollow and exploitative in nature. “Only the Brave,” which chronicles an Arizona firefighting crew known as the Granite Mountain Hotshots from their early days struggling to get certified to their tragic encounter with the Yarnell Hill fire, has been made with a combination of sincerity and technical skill that is effective on a fundamental level, even if it never quite becomes the devastating emotional experience that it clearly wants to be.