N.T. Wright's wise words in How God Became King:
The reason the Enlightenment has taught us to trash our own history, to say that Christianity is part of the problem, is that it has had a rival eschatology to promote. It couldn’t allow Christianity to claim that world history turned its great corner when Jesus of Nazareth died and rose again, because it wanted to claim that world history turned its great corner in Europe in the eighteenth century.
“All that went before,” it says, “is superstition and mumbo-jumbo. We have now seen the great light, and our modern science, technology, philosophy, and politics have ushered in the new order of the ages.” That was believed and expounded in America and France, and it has soaked into our popular culture and imagination. (George Washington contrasted the “gloomy age of ignorance and superstition” up to that point with the new epoch ushered in by the great revolutions of the late eighteenth century, when “the rights of mankind were better understood and more clearly defined.”)
So of course Christianity is reduced from an eschatology (“This is where history was meant to be going, despite appearances!”) to a religion (“Here is a way of being spiritual”), because world history can’t have two great turning points. If the Enlightenment is the great, dramatic, all-important corner of world history, Jesus can’t have been. He is still wanted on board, of course, as a figure through whom people can try to approach the incomprehensible mystery of the “divine” and as a teacher of moral truths that might, if applied, actually strengthen the fabric of the brave new post-Enlightenment society.
But when Christianity is made “just a religion,” it first muzzles and then silences altogether the message the gospels were eager to get across. When that happens, the gospel message is substantially neutralized as a force in the world beyond the realm of private spirituality and an escapist heaven. That, indeed, was the intention. And the churches have, by and large, gone along for the ride.