I have read that, before his death, Martin Luther protested that Mary was no more holy than any other son or daughter of Adam, no more holy than himself.
Is Nestorianism at the root of Lutheran Protestantism?
This was condemned by the Catholic Church at the Council of Ephesus, in 431. The child Mary gave birth to was true God, a Divine Person, without sin, without concupiscence, being one person both God and man. Nestorius claimed that there were two persons in Christ, not one, a divine person and a human person, and that Mary was mother only of the human person. Jesus, the human being was not God, denying Jesus’ divinity, thereby denying we may invoke Our Lady. She is not, he believed, the Mother of God. So she doesn’t have any more influence than you or I with Him.
Catholic’s believe she is the Mother of God, the dignity and power Mary has before her Son comes from the fact that the child she conceived and gave birth to, though having a human nature, nevertheless was God Himself.
In the Hail Mary we say “Holy Mary, Mother of God, pray for us sinners.” We don’t think Our Lady, or the saints, or the angels are somehow substitutes for God. We are asking them to intercede for us.