Jesus is God come down from heaven. His conception, itself, demonstrates collaboration between the divine and human; however, it is both initiated and empowered by God. Given his unique identity, it was logical that his earthly beginnings should reflect this great mystery. He would not be conceived like other men.
Many modern-day versions of Christianity attempt to jump-start the faith and ignore the 2,000 years of Catholic faith and tradition. Oftentimes, this means that they will struggle through the various heresies which the true Church long ago put to sleep: as with Arianism, Nestorianism and Gnosticism. The role of Mary has been a great safeguard for orthodoxy. Separated from the protective influence of the Holy Spirit over the Magisterium and discounting Mary’s place in faith and devotion, these new attempts at Christianity are almost certain to fail. Believers might be very sincere, but errors in doctrine are certain. Jesus is not almost God but God himself. He is not a creature (Arianism). He is the Word made flesh. Jesus is not a ghostly entity pretending to be human (Gnosticism). He was conceived, born, suffered and died. Jesus is not a human person, but is divine with human and divine natures (Nestorianism). Mary is the Mother of God, not merely the mother of the man. There are not two sons and Christ’s sonship is unique and eternal (against Adoptionism).