Marian apparitions

In Catholicism, there are different kinds of visions and apparitions, including Christophanies and angelic apparitions. Jesus is said to appear to famous Catholic mystics. 

Reputed Marian apparitions occupy a central place in Catholic piety. But that raises question: What niche do Marian apparitions fill that isn't already covered by Christophanies and angelic apparitions? If, according to Catholicism, Jesus can and sometimes does appear to people, aren't Marian apparitions inferior and superfluous? What distinctive purpose do Marian apparitions serve if some people have visions of Jesus?

It might be countered that God often works through intermediaries. But isn't that a function of angels? If it's a question of supernatural emissaries, angels already play that role.

Catholics say Mary points people to Jesus. But even if that were the case, why are most reputed apparitions visions of Mary rather than, say, visions of St. John the Evangelist? Isn't St. John the Baptist well-positioned to point people to Jesus? Why aren't there more Catholic reports of St. John appearing to people? "I'm the Beloved Disciple. I was the closest confidant of Jesus. I was an eyewitness to more of his ministry than anyone else". 

Moreover, angelic apparitions or apostolic apparitions wouldn't draw attention to themselves in the way Marian apparitions do. People know that angels are merely creatures, and apostles are merely emissaries. 

By contrast, reputed Marian apparitions draw attention to herself. She (allegedly) tells San Juan Diego to build a shrine to her–not to her Son.

She (allegedly) introduces herself to Bernadette as the Lady of the Immaculate Conception, and to Lúcia, Francisco, and Jacinta as the Lady of the Rosary. That draws attention away from Jesus. 

It's striking that the catalyst for Christian revival in the Muslim world is dreams and visions of Jesus rather than Mary. And that makes sense. Between visions of Jesus and visions of angels, there's no niche for visions of Mary.