It's a technology demo created by techies. And now you want a (good) plot as well? You should just be thankful it isn't about Harry Potter defeating Darth Vader!
Actually iirc, BBB was about developing the hair system in Blender. Also, the movies aren't about just copying something existing out there already, but to give a lucky few that are interested in a particular area (directing, story boarding, concept art, musical score, etc.) a chance to wet their feet on a project and show their skills off to the world and maybe even land a job working for the "big boys" (like how Ian Hubert now works at Pixar thanks to Tears of Steel).