1. Mary was blessed among women, true. Anyone selected to bear Jesus was blessed, of course.
2. As pointed out already, 'all' have sinned and fallen short. No exception is made in scripture for Mary or anyone else.
3. Mary is a central figure during the nativity, and she plays a key role again at the cross.
4. However, Mary is only mentioned at two other places in the gospels. In both of these her appearance is fleeting and Jesus, in all honesty, seems to be even a bit dismissive of her. Matt, 12:46-50; John 2:4. On both occasions he has the opportunity to heap praise upon his mother and encourage others to do the same. It didn't happen.
5. What always has struck me is that in all of Paul's epistles and those of others Mary is not mentioned once. If she were so central in the worship and theology of early Christians, why would she be completely omitted? This suggests to me that Mariology grew and grew in the centuries that followed.
6. The dogma of the Immaculate Conception was not, of course, defined until 1864 by Pius IX, the author of the "Syllabus of Errors". It was when Pius IX was Pope, too, that papal infallibility in matters of faith and morals became a required dogma. There seems to be no Biblical basis for either of these doctrines. The Bible doesn't even mention the parents of Mary.
7. The dogma of the the Assumption was not defined until 1950 by Pius XII. There appears to be no Biblical basis for this either. Like the Immaculate Conception, it appears to be a theological construction - one doctrine piggybacking on another and another and another..
There is much more that could be said - books, indeed - but no one is attacking Mary. She is revered for her relationship to Christ. The question is: has Mariology as it developed in the church been justified? So much of it - so many apparitions, for example - seem invalid. Even the church dismisses most of them as doubtful or false.
But for those who venerate Mary, fine. For those who don't, that's okay, too. Why can't Christians agree to disagree and leave it at that? God bless them all.