I read through Mater Populi Fidelis. Overall, it is a solid document. Since the Dicastery for the Doctrine of the Faith issued the document and with the Pope's approval, in accordance with Donum Veritatis 18, it would fall in the Ordinary Magisterium and fall "in forma communi."

Now, it mainly serves to deepen and clarify our understanding of Mariology. Part of the development of doctrine in line with heremeneutic of continuity for doctrinal consistency, unity, and integrity. A precise term, homogeneous evolution of doctrine.

As for the controversies, this is my understanding:

-Co-Redemptrix and Mediatrix of All Graces: discouraging usage due to the confusions and various explanations (prudential decisions)

-Mediatrix: can be used but with caution- Our Blessed Mother having a subordinate role