Francis: Our Lady Was “Not Co-Redemtrix” – Although Pius X, Pius XI, John Paul II Said It
He vilified introducing new Marian titles and dogmas a “foolishness.” The Church existing before Francis introduced hundreds of Marian titles (e.g. in Marian litanies) and proclaimed four Marian dogmas (Mother of God, Virginity, Immaculate Conception, Assumption).
Attempts to proclaim the fifth Marian dogma of the Co-Reedemer were strong throughout the 20th century but Pius XII vetoed them although this title has been used and discussed since the 15th century.
Pius X invoked it in a prayer which is part of an official Church document (AAS  1914, 108). The title was also used by Pius XI and John Paul II.