Church Fathers, Saints, and the other examples above are “not infallible”.
This argument is also in vain as we can clearly see from the definitions of the Magisterium above that when a teaching of the Church is unanimous, it is part of the Ordinary Magisterium of the Church, which is itself infallible, according to the solemn teaching of the First Vatican Council. Certainly, when a theologian speaks or writes on a doctrine, that in itself is not an infallible statement; it is when that doctrine is unanimously taught elsewhere in the Church without condemnation that it becomes part of the infallible Ordinary Magisterium.
Furthermore, to say any of the sources above are “not infallible” is to directly imply that they have been in error for all the years or centuries since they were allowed to propagate, and that the Solemn Magisterium did nothing to correct it. This is to say that the Catholic Church can propagate error and heresy, which is a denial of the dogma of the Infallibility of the Church. It is blasphemy to say the One, Holy, Universal, and Apostolic Catholic Church can introduce anything harmful to the faithful.
Church teaching on the subject: Pope Pius VI in Auctorem Fidei, 1794, condemns: ''the Church, governed by the Holy Spirit, could impose a disciplinary law that would be not only useless and more burdensome for the faithful than Christian liberty allows, but also dangerous and harmful" (again, this was condemned). Also, Pope Gregory XVI in Quo Graviora (1833) states, "The Church is the pillar and foundation of truth, all of which truth is taught by the Holy Spirit. Should the church be able to order, yield to, or permit those things which tend toward the destruction of souls and the disgrace and detriment of the sacrament instituted by Christ?”