Despite the millions of pilgrims gathered in Rome, attendance at weekly Mass in many places has declined and many have left the flock. By Larry B. Stammer, Times Staff Writer ROME — Only a few miles from the throngs that pressed into St. Peter's Square to bid farewell to Pope John Paul II, a soaring Baroque-style basilica echoed with emptiness. Inside, 20 of the faithful were sequestered in a side chapel for the noon Mass, while Father Virgilio Missori, 84, sat alone near a confessional booth awaiting penitents who did not come. In many ways, the quiet scene day in...