The Museum of Modern Art’s Matisse Picasso show gathers up lots of great paintings. “With sixty-seven mostly top-drawer paintings, drawings, and sculptures by Picasso and sixty-six by Matisse, the show hardly needs a pretext, but it has one: a running dialogue of mutual attractions and abrasions between the twin godheads of modern painting. But to extract the story—an elliptical tale, full of hints, puzzles, and fine discriminations—while looking at so much stupendous art is like trying to check the oil in a speeding truck.”