He changed the title because There and Back Again is the name of the book Bilbo writes telling the story and he didn't want the title of 1/3rd of the trilogy to represent the whole story. Especially since the battle of five armies is the biggest and most important aspect of the end of the story... So what's so bad about the title?
Im gonna be that guy, if you read the source material you would understand. "Battle of Five Armies" is what Tolkien called it after all.