The Sundance Film Festival is fighting a battle that’s been building for several years, and what it’s fighting for can be summed up in one word: relevance. What makes a Sundance movie relevant? In a sense, the old criteria still hold. It’s some combination of box-office performance, awards cachet, and that buzzy, you-know-it-when-you-see-it thing of penetrating to the heart of what we used to call the conversation.