<> Christian Doctrine has always been 100% truthful and bereft of any exageration. That is to be expected from the Church Jesus established to Teach all nations. The Triune God would not allow error or exageration to be taught as Doctrine.
It is true thqat individual Christians do err and due exagerate about certain aspects of Doctrine. That is to be expected. They have no Divine guarantee they will be infallible. I am not sure which exagerations made about Mary you might be referring to<>
It seems to me the main reasons for their denial of (Marian doctrine) aren't theological reflections, but a need for self-definition by way of differentiation.This is jmho of course.