There’s nothing wrong with epics, per se, but every movie about the slave experience doesn’t have to be a 145-minute Oscar hunter. There’s plenty of other stories, and storytelling conventions, and it’s nice to see Hollywood starting to diversify artistically in its effort to be culturally diverse. “Emperor” (2020) is an action movie set in the pre-Civil War South about a slave, Shields Green, fleeing a murder rap. Dayo Okeniyi plays Green. From the beginning scenes on the plantation to the climax at Harper’s Ferry, the story is tight and compelling. Who cares whether it’s “based on a true story?”