When you read the works by C.S. Lewis and Dorothy Sayers intended for popular consumption you can tell they have read and understood Nietzsche, Freud, and Hegel. You will hear echoes of the philosophies of Plato and Aristotle, and the theology of Augustine and Aquinas.
When you hear many modern-day sermons you hear echoes of Osteen, sitcoms, popular movies, motivational speakers, and books written by professional coaches.
I wonder why the modern American church is largely unprepared for the challenges it currently faces?