If what you say here is true–that only God can impart wisdom then no one could read books by theologians or listen to sermons or be taught by another person. The difficulty is that you have no knowledge of the Communion of Saints, what that means and how it affects the lives of those still living on the earth.
Those who have gone before us to heaven are not dead, but alive. Jesus specifically stated this. St. Paul tells us we are all one in the Lord–those on earth as well as those in heaven, whom he called a “great cloud of witnesses”. Jesus spoke with two “dead” people and consulted with them on the Mount of Transfiguration. The problem isn’t that heavenly persons cannot speak to us or help us, but that you have not been taught this truth and so it is alien to you.
When an ambassador comes from another country representing his government he speaks for it and for his people. We are all “ambassabors for Christ”, both we who are living on earth and those in heaven. We listen to our ordained and those trained to teach us, how much more should we listen to those who are alive with Christ in heaven, whom he sends to remind us to repent, to avail ourselves of all the helps to salvation he has given us, to live holy lives devoted to his service? That is what Mary tells us by saying God wants her to be known and loved. She is his ambassador whose whole being is dedicated to him and to giving to us men what God has given to her to impart to us–just as anyone else, alive on earth or alive in heaven can do through the power of the Holy Spirit. For it is only through the power of the Holy Spirit that we can do anything of value for God.