Every year, like cicadas and Europeans, the art world disappears in August. But before that, New York galleries traditionally stage a group show—usually modest, often thematic, and occasionally, miraculously good. In recent years, though, dealers and critics have lamented that these shows feel timid, incoherent, or like thinly veiled attempts to offload unsold inventory. Some have wondered if the group show is fated to die out altogether.