Ron Howard’s “Eden” opens with a bold statement: “Fascism is spreading.” It’ll surely carry weight in modern society, but the phrase is referencing events from nearly a century ago. Based on a true story, “Eden” retraces what happened when a group of Europeans attempted to start anew on the remote island of Floreana, only to encounter the earthly failings they hoped to escape: chaos, blackmail, betrayal and even murder. Howard assembles an impressive cast, though it isn’t always enough to make up for the overambitious plot of a film that drags in the middle. 1920s Germany, haunted after accepting blame...