St. Augustine, like many church fathers and doctors was never the pope.
Like Origen and Tertullian and others not quite as famous, the pope, speaking ex cathedra, has the final word on what is truth and what is not.
This is one of the things I love most about the church, and that is that I can trust that once all the theology has been studied and sifted through, the church will infallibly state what is truth and what is not.
How else could Jesus have fulfilled His promise that the Spirit would lead us to all truth and that the gates of Hell would not prevail against His church?
It is impossible for everyone to be right when thousands of interpretations contradict each other and the Word is used as a weapon against others rather than as the testament it is meant to be.
Protestants will not / cannot comprehend the structure of the Church because they see it through the lens of their own limitations. Within the Church it is the ideas advanced that have stature and importance and, like all endeavors sincerely interested in the truth, every idea is pushed to its extremes by peer review and testing. There is no shame for actions and positions taken in the search for the truth, even when one is publicly wrong in the process.
In contrast, Protestant dogma is dictated by a self anointed few. Protestant emphasis is on gaining personal glory and followers by finding or creating the hidden decryption keys planted by God within Scripture to ensure that only the chosen elect, clever enough to "get it", gain salvation.
We catholics are truly blesses that within the Catholic Church the Holy Spirit is allowed to speak, guide and correct through a consensus developed over thousands of years.