THE NEW YORKER'S David Denby doesn't like "Sicko." That was a shock. In this film Michael Moore seems to have come of age as a film-maker and a man with a message. Of course, there were gimmicks, like the boat ride to Cuba. But all communicators use gimmicks. If they work they're called brilliant strategies. All of Moore's gimmicks, going back to following GM's Roger Smith, have worked. This batch work more smoothly. Especially brilliant, as THE NATION's Christopher Hayes points out, is Moore's tracing the health-care mess back to emerging conservative Ronald Reagan.