Very simple.2Peter,2,3John,Jude,James,Hebrews and Revelation were NOT Canon at one time.They were not even recognized.They were not considered scripture at one time.Very simple.They needed to be decided on.All 27 books were written by 100AD.There would be no need of Catholic Councils if they knew this was the canon immediately in 100AD.The Church decided.Very simple.
The Church's Canonical declarations did not make these books Sacred Scripture, it is true, but it infallibly declared them so. In the face of so many spurious epistles & false Gospels, only the Church could have discerned (because God was/is with her) what was Sacred & what was not. That is Jim's point.
Of course, Church Tradition predated & played a crucial role in the Canon of Sacred Scripture.