Religion is a subset of ideology, and ideology is a set of beliefs about how how the world is and how the world should be. Capitalism is an ideology. Communism is an ideology. Scientism is an ideology. Christianity, Islam, Buddhism, Hinduism, Sikhism and so on are religious ideologies.
The boundary between the two is weak. Communism and Scientism make metaphysical statements. Communism and Scientism generally state that there is no soul, there is no afterlife and there are no supernatural beings.
Capitalism believes that people, out of self interest (greed and selfishness), act in ways that create welfare for the majority. This is a radical belief, held by almost no one and no other belief system in history. It also believes in unlimited growth. The combination of these beliefs is going to wind up killing a few billion people.