That may be your Protestant perspective, but plenty of Protestants are fully on board with the definitions of the Second Ecumenical Council, and endorse the titles of "Mother of God" and "Theotokos" for Mary. Among them you'd find Martin Luther and lots of company.
Been reading an interesting book on early Christian theology. As originally expressed in the Greek, Theotokos can also mean "Bearer of God" (as in she bore a child), which doesn't have quite the same implications in English as "Mother of God".
Mother of God can lead to a lot of misunderstandings unless you know the exact definition and reasons the term was coined in the first place.