C.S. Lewis believed that there is a physical realm and a spiritual realm, with many battles taking place, unseen by human eyes, yet still having a great effect on us. Lewis did not view ideas such as "sin" and "wickedness" to be outdated or obsolete. All that the modern era has to offer, the technological progress, equality campaigns, humanistic utilitarianism, and so on have not solved the world's problems. We still have wars and crime. There is still extreme suffering. Yes, there have been major breakthroughs in liberties (the abolishment of slavery, the destruction of corrupt governments, etc.), but society as a whole does not seem to be gaining ground in the areas of moral growth, or even happiness.
Some might say that religion is one of the causes of constant hostilities, therefore if we got rid of religion, then we would eliminate a major factor in human conflict. It would be just as easy to do away with love, or a justice system! As long as there are humans, there will be human emotions, thoughts, and beliefs. Humans have a particular knack for finding something to intensely focus on in their lives. Whether it is an object or idea outside themselves, or their own self, everyone has something they "believe" in. Any sort of creed or "-ism" fits the bill: environmentalism, naturalism, Christianity, Mormonism, atheism, agnosticism, Islam, Judaism, materialism, Catholicism, postmodernism, spiritualism, Wicca, minimalism, feminism... the ways of thinking are endless.
In the end, everyone has a theory of who they are, how they got there, and what they are on planet earth to do. Some people just throw their hands up in the air saying, "who knows!" or "does it matter?" But you'll find those people, too, are wrapped up in something they value, whether it be a cause, a life-style, or personal gain. That is their religion. So it is foolish to say that we can "get rid" of religion. It is much more beneficial to focus on ending the hostility between religious factions. Even if I have a different faith than my neighbors, that does not give me the right to kill them.
Lewis described the world as being "invaded by powerful evils bent on destroying all that is good". He saw the message of Christianity as the truth that would set the world free. While he clearly had a strong imagination, as seen in his books about Narnia, he was also a practical theologian. His book "Mere Christianity" is a rational exploration of the basic tenets of the Christian faith. I am excited to re-read his thoughts at this time; I first read the book several years ago during college but didn't have much time to seriously ponder anything. This will be a good journey.