Protesters Why were the Early Protestants still venerating Mary to an extreme? The answer lies in the very word, Protestant. These men were in the main all ex-Catholic priests. They had been steeped in the Catholic doctrines and teachings, and Customs, and Traditions of Catholicism. But they began to disagree with what they had been raised in, and protested vehemently on what they considered so important.
However they did not dump everything 100% because they were used to all the trappings of Rome, but rather focused on what they considered the essentials of the Christian faith. The history of Protestantism is one of a gradual coming out.
Later in history, the other minor doctrines came under fire by succeeding Protestants who, by this time, never had ties to Rome. They never had been Catholic. These biblical scholars were distant from the trappings of traditional Catholicism. So it was easier for them to downplay the Veneration of Mary without any qualms.
To them Mariology became to be Mariolatry, a type of idolatry. They recognized Mary's own confession of a need for a Savior, in her Magnificat (Luke 1:46-47) so she could not have had an Immaculate Conception. (See also Romans 3:23)
It was in proportion as to how far away from the Roman Church (as well as how far from the initial Protestation era) that modern Protestants distance themselves, that Mary becomes insignificance, especially in her alleged role in a person's salvation. (Acts 4:12 Neither is there salvation in any other, for there is none other Name under heaven given among men, whereby we must be saved.)
Most modern Protestants have never had any contact with Roman Catholicism, so the doctrine of Mary is quite foreign to them, and is considered non-essential to the Christian life. Their focus is solely on the awesome Lord and Savior, Jesus Christ!