Francis Ford Coppola on Thursday premiered his self-financed opus “Megalopolis” at the Cannes Film Festival, unveiling a wildly ambitious passion project the 85-year-old director has been pondering for decades. Reviews ranged from “a folly of gargantuan proportions” to “the craziest thing I’ve ever seen.” But most assuredly, once again, Coppola had everyone in Cannes talking. No debut this year was awaited with more curiosity in Cannes than “Megalopolis,” which Coppola poured $120 million of his own money into after selling off a portion of his wine estate. Not unlike Coppola’s “Apocalypse Now” some 45 years ago, “Megalopolis” arrived trailed by...