I am confused by this statement. Does Father Hart mean within Christianity overall (i.e. the Reformation has exhausted its usefulness), within Catholicism (Anglo-Catholics, Roman Catholics and Eastern Orthodox Catholics need to settle our differences) or within Anglicanism (Anglicans need to understand our Catholicity and as a consequence get over this low church thing) or something else?
Father Hart is speaking about the Anglican Province of Christ the King. The Affirmation of St Louis was the foundational document for the Anglican exodus from ECUSA in the late 1970's.