The eldest millennials turned forty this year, and the producer Ngofeen Mputubwele comments on a sense of despair he finds in his generation, having to do with the state of the planet, the nation, the Internet, intolerance, and more. He set out to explore why millennials feel hopeless and how they can live with that feeling, in conversations with five writers: Kaveh Akbar, the author of “Pilgrim Bell”; Carlos Maza, the creator of the video essay “How to Be Hopeless”; Shauna McGarry, a writer on “BoJack Horseman”; Patrick Nathan, the author of “Image Control: Art, Facism, and the Right to Resist”; and the climate activist Daniel Sherrell, whose recent memoir is “Warmth: Coming of Age at the End of Our World.”