If religion is about the sacred as opposed to the profane, the spirit as opposed to matter, the Creator as opposed to the created, Confucianism plainly does not qualify. But perhaps what we are to learn from this tradition is not that Confucianism is not a religion but that not all religious people parse the sacred and the secular the way Christians do.
Stephen R. Prothero, God Is Not One: The Eight Rival Religions That Run the World--and Why Their Differences Matter
christianity, confucianism, religion, spirituality