What the Angelus reminds us of
Fr Leo J. Trese tells us in page 79 of The Faith Explained
Because it was by her own free consent that Mary chose to be the mother of the Redeemer, and because it was freely (and so intimately!) that she shared in His Passion, Mary is acclaimed by the Church as the Co-Redemptrix of the human race.
It is this grand moment of Mary's consent and our own salvation that we commemorate each time that we recite the Angelus.
The beauty of reciting set prayers.