For Eliot, one of the single greatest causes of Western civilization becoming "The Waste Land" is the fact that religion doesn't really have the influence it once did. In the old days, people didn't have to worry so much about questions like "Why am I here?" or "What's the meaning of life," because religion already had answers for these questions. In the modern world though, Eliot has seen a decline in the power of religion, and one of the side effects of this decline is that more and more people are feeling like they're in a funk or suffering from a full-blown spiritual crisis.
"The Waste Land" suggests that most of the world's problems would go away if we all found religion.
Deep down, Eliot doesn't really believe in any God or higher power; he just likes the comfort that he gets from religious stories.