Men have crowded all her glory into a single phrase: The Mother of God. No one can say anything greater of her. ~ Martin Luther
Mary is the Mother of God.
Sometimes Protestants don't like to hear that. Even on our Lutheran Calendar, we call this day of her commemoration, "Mary, Mother of Our Lord" rather than "Mary, Mother of God"
But if you have any understanding of the Holy Trinity or even of the Incarnation, you have to confess Mary as Theotokos, or "God Bearer" as the Church did at the Third Ecumenical at Ephesus in 431.
Protestants sometimes veer off into ancient heresies with simplistic formulations like Mary was the mother of the human part of Jesus and God was the Father of the Divine part of Jesus. BUZZZ! WRONG!! Jesus is fully human and fully divine and Mary carried the whole Jesus, God in Flesh in her womb. If you don't get that , you need to go back and study your church history, Nestorius in particular, because he had the same problem. His side lost. The Church, in her wisdom, decreed that you cannot separate Jesus into a human and divine part.
Unfortunately I don't think today's problem with thinking of Mary has anything to do with confusion about the nature of Christ. People would actually have to have some theological background for that. I think it's partly our discomfort with the whole idea of Incarnation. Of God actually being in a womb and being born in blood and pain and messiness. We are always trying to keep God out of the messiness of our lives. Far better to keep God off far away - because then we can imagine we can leave the messiness of this world to get to God, rather than accept that God comes to us in our messiness.
There may be some sexism involved in the push to diminish Mary's role in our redemption. God forbid there be anything female about God or salvation. Although I haven't noticed that that either the Roman or Eastern church, both whom highly exalt Mary have been particularly respectful of the role of women who aren't both virgins and mothers.
I always enjoyed the way Sojourner Truth ended her famous "Ain't I a Woman" speech:
Then that little man in black there, he says women can't have as much rights as men, 'cause Christ wasn't a woman! Where did your Christ come from? Where did your Christ come from? From God and a woman! Man had nothing to do with Him.