The makers of the influential 2008 documentary “Food, Inc.” never planned to make a sequel. They figured they’d said it all in their harrowing look at a broken, unsustainable food system — a system led, they argued, by a few multinational corporations whose monopoly squeezes out local farmers, mistreats animals, workers and the soil itself, and makes all of us less healthy. But 16 years after that Oscar-nominated film, they’re back with “Food, Inc. 2.” What happened? Well, first of all, the pandemic — an event that both strained our food system and revealed its precariousness, they say. Also, the filmmakers suggest, it was perhaps naive to assume that informed, ethical shoppers could alone reverse such an entrenched narrative. “You can change the world with every bite,” the first film had argued, urging consumers to buy local and organic, patronize farmer’s markets, demand healthy school lunches and most of all, read labels and understand what they’re eating.