Three things stand out about the current edition of “Greater New York,” a survey at MoMA PS1 of artists living and working in New York, which happens every five years: pitch-perfect politics, intense nostalgia and an underwhelming display of new art. Organized by a curatorial team led by Ruba Katrib, “Greater New York” — which opened Thursday — is both a show of our moment and one that attempts to escape it through the trap door of history. In the art world at the moment, it’s safer to celebrate the underknown, underrecognized and under-acknowledged artist who was radical half a century ago than to dive into the actual messy politics…