Suppose there are no reasons that authorize the cannonization of certain texts or privilege certain texts over others. Then either the church fathers made a mistake or they chose arbitrarily. The huge controversies and disputes at various church councils into the 6th century give us good reason to rule out the latter. If they simply made a mistake because there are no such reasons, then we are in no better a position to adjudicate between texts than they were. Furthermore, if God reveals truth in the scriptures, but does not furnish us with reasons to adopt certain texts as scriptures, then God has not revealed truth to us in scriptures. No one among us is authorized to dub one account true and another false. This option looks pretty hopeless.
Suppose there are reasons to cannonize certain texts or privilege them. To whom might they be revealed? I think it would be plausible that every rational being could possibly come to know these reasons, in the way that it is possible for every being capable of learning a language to learn Spanish. Certain concrete limitations that come into play and the way a person is situated in life shape the contours of the language-learner's actual ability to speak Spanish. Perhaps I never learned or heard the sound of a rolled "r" and then tried to roll my "r's." This would function as a constraint on my ability to speak Spanish at the time. So our current situatedness in the twenty-first century, our distance from the original texts and lack of fluency in the original language constrain our ability to understand or come to know the reasons for privileging certain texts as scriptures. We leave this to the experts who are in circumstances that make them experts; in the case of texts written thousands of years ago, it seems that the early church councils, being only a few generations removed from Jesus' time at the most and many having fluency in the languages of the original texts, are better situated than us to adjudicate which texts countenanced the truth.
The role of the Holy Spirit in this process as well as the effect the Holy Spirit could have on far-removed present day students of the scriptures would be another interesting avenue to explore.