In their forthcoming book, “Beyond Doubt: The Secularization of Society,” the sociologists Isabella Kasselstrand, Phil Zuckerman and Ryan Cragun describe a change in the built environment of St. Louis that is “emblematic” of the ebb of organized religious observance in America. What was once a Gothic-style beauty of a Catholic church built in the 19th century by German immigrants had been turned into a skateboard park.