Why, there is sufficient scriptural evidence that St. Luke and St. John at least were firsthand familiar with the life of Our Lady; we know from scripture that she was with the other apostles as well at Pentecost. St. Justin Martyr (early 2c) offers the cornerstone of all orthodox mariology -- the symmetry between Mary and Eve -- which only works if Mary is completely free from sin. If the Holy Tradition did not supply that knowledge to St. Justin, he had no reason to invent it and risk someone proving him wrong.
We are never going to resolve these differences
Thousands of converts from Protestantism each Easter prove otherwise.
The Catholic population as a percent of the total is declining, so what does that tell us? Popularity is not a proof one way or the other.