I really recommend you understand that the Early Church Fathers were NOT infallibly inspired to declare that everything they taught was the truth. That is why God GIFTED us with the Holy Scriptures. They are what are infallibly inspired.
you are correct they were not infallibly inspired, but what they do testify to is the universal Faith that was handed down by the Apostles. so you see the same Faith in Corinth, as in Jerusalem, as in India, as in Rome, as in Alexandra, etc. We also know that Jesus promised the Holy Spirit to guide the Church into all truth and we also know that all the groups who weren’t part of the Catholic Church, denied the deity of Christ or taught other heredical teachings. they also testify to the Catholic Faith, and we can clearly see it’s doctrines in their writings. think about it, 1,500 years is a long time for The Church to be teaching heresy before the reformers showed up.