So, are Catholics who deny that sola Scriptura is valid, not REALLY true practicing Catholics? They certainly are denying the teachings of the (reputed) early church fathers.
It certainly is the official position of the Roman church.
True Catholics (universal) would read and obey the written scriptural warning not to ADD to the Word.
Offcourse, not everything the church fathers wrote was scriptural, but their position on scripture as being the only infallible source of doctrine is clear.
FWIW, I think you've fallen into the error of believing that the theologians who were so prominent in the generations immediately following the end of the Apostolic Era were "Catholics". They were catholic in that they were united by their faith with all other Christians, but they were not subjects of a hierarchy. Thus they were among the universal body of believers, but not a RC hierarchy.
Offcourse, not everything the church fathers wrote was scriptural, but their position on scripture as being the only infallible source of doctrine is clear.
Do you think their attitudes about Scripture were a reflection of Christians in general during this time?
It seems obvious to me that the Holy Spirit was guiding them in recognizing what was Scripture and what wasn't.