My approach is to assume that the magisterium of the Church (as stated by then Cardinal Ratzinger) is right, and to form my understanding of the Vatican I requirements for
ex cathedra statements around that magisterium. So it is clear to me that it must be the case that one or more of those Vatican I requirements was not met in the case of
Ordinatio Sacerdotalis.
It seems to me that the missing requirement was the lack of the intent by the Pope to bind the universal Church to an
ex cathedra statement. Archbishop Bertone
explicitly mentions the Pope’s intent in assessing the infallibility of his teachings (bold added):
Thus,
Ordinatio Sacerdotalis is not
ex cathedra because Pope John Paul II did not
intend it to be. It is similarly clear that Pope Paul VI did not intend
Humanae Vitae to be
ex cathedra.