Forgive me if I continue to dance around the question without trying again to address it "full on". I guess I'm hoping that the sentences used to flesh out the question will evolve to a place where I think I can say something useful and direct.
Anyway, I think we are presented with two phenomena: (1)Cult of saints, especially Mary; (2)Controversies.
I would venture to say that both of these arose sort of independently of the development of the canon of the NT. And nobody was saying, Hey! We need to check this stuff with the Scriptures and only the Scriptures.
The controversies, starting with the Gentile circumcision controversy, established the Church as the bearer (or the speaker? conduit?) of an unfolding (developing) revelation. (Why weren't the Bereans called upon as "periti", experts, in the Council in Jerusalem?) What does it mean, if anything, that the Bereans are singled out for this description and notice?)
There is a discontinuity in the Biblical record, but why must we think that there was a discontinuity in the life of the Church. It is only after the Reformation tht we look back and say, Hey! Looka that! The Council of Trent closed the OT canon! But the Church for all those hundreds of years wasn't fretting about the OT canon or thinking it must be closed, not until there was a controversy.
And presumably the Church knew about the Bereans and their study of the OT to see if Jesus was the Christ. But it was only sporadically (as far as we know) that people suggested that should be the only way to study, and that it should be expanded to include the NT.
So I think the question about the Bereans and the now suggests what may be a false picture and a false discontinuity.
This is kind of smrt-alecky, but I think it's important:
Are we so different than the Jews and Greeks of Paul’s time that we need more interpretive aids than they did?
Well, there's the NT. Do we complain about needing THAT interpretive aid?
Please don't give up on me. I think we may be able to get somewhere.
FWIW, by the middle of the 4th century, +Ephrem the Syrian was describing Mary as "sinless" and immaculate. Ambrose and Augustine used similar language, though not specifically saying she was sinless from conception.
My point is not "So it MUST be true," but rather to say that, despite the saying of some that Augustine was an explicit believer in Sola Scriptura, these guys were not so greatly troubled by appealing now to Scripture and now to Tradition as some are these days.
Yesterday evening at Mass, my pastor said in his homily that Ephrem said the sinlessness of Mary was a tradition from the Apostles. FWIW. I can find nothing like this on line but absence of evidence is not evidence of absence and evidently not all of Ephrem's work is on line yet
Now if we're going to assume for other reasons that the great apostasy happened at or around Nicea, this could be taken as evidence: A lying Syrian deacon whom tradition places at Nicea, fall even deeper into sin and apostasy by making up this so-called tradition. The winners write the history, and so there you have it.
But if we don't take recourse to that blanket condemnation, we have evidence of writers for whom the appeal to tradition was meaningful and not problematic epistemologically.
I was musing yesterday during my 80 miles of motor scootering hither and thither that what "the world" sees of the Catholic Church looks to 'the world" like pageantry and legalism.
But simple worship makes lousy TV or Movie footage, and the chaste liturgy I experienced among Trappists in Missouri is not as cinematic as some more elaborate stuff. The world is not going to see a simple, quiet morning Mass unless the world gets its behind into the church to look.
And I conjecture that the appearance legalism arises from an attempt to systematize and organize several centuries worth of ad hoc decisions, acts taken in response to problems and disputes.
And this systemization is precisely to avoid the grounds for the other perception of the Catholic Church, unbridled and dictatorial exercise of power. Having worked for a sheriff who would lay down a dictum as for the ages this year, and the following year act like he never said any such thing (to be fair, I think it possible that his memory was beginning to go), I appreciate that the mere record of acts is a kind of check on the otherwise capricious and unbridled exercise of power. As citizens of a nominally democratic republic, we may not appreciate constitutional or traditional limitations on the exercise of power in other forms of government. But it is useful to recall that the 15th or 16th century yeoman of England considered himself a free man under a king.
Systematization and laws have to do with a dialectical tension between obedience and freedom. Where there is no systematic presentation there is little freedom (in the secular sense, because the authority or power center can say, I don't care what we said or you heard yesterday, NOW I tell you to do THIS, and you must do it." But I digress.
Arising out of the 13th and 14th century universities of Paris and Bologna, and other such institutions I think we can see that there was a growing interest in an orderly and systematic presentation of the truths of the Faith. While it's good to tidy up around the edges off things, I personally think it can be carried on too far.
Especially in matters of the heart, in relationships, between now and the eschaton, there are going to be loose edges.
And, believe me, having been on the outside looking in, I GET the appearance of legalism. But on the inside, and as that weird hybrid, a "lay religious", I have to report it's not like that. There IS a certain discipline to praying and reading Scripture (at least a little bit) 4 times a day (more when I can) AND going to Mass and praying a Rosary almost daily. But it's more like the discipline of wrestling 4+ matches a day or maybe being a physician and seeing 4+ cases a day. Every time it's different.
Say there was a rule that you have to talk to your spouse 4+ times a day. Today might be boring, or it might be the day when she says, "If you leave the toilet seat up one more time I will tear you limb from limb," or he might want to say, "I just wanted to tell you that, taken all in all, you have been a great gift from God to me, and I thank God for you and I thank you for you," OR, [moment striking terror into the heart of every male] she might say, "I think we should talk about our relationship." Even if this encounter, of a string of them is dull, that dullness is itself interesting and important.
And, to use a well-worn metaphor, it's like the rules of a sonnet. They don't prohibit spontaneity, they channel and focus it and magnify its energy.
YES it's possible to write a glib sonnet. I did once. So it's possible to keep God at arm's length. But that is the fault of the worshipper, not of the worship.
But my alleged point is that one could say the POINT of a Church is not to have a reliable, systematic, comprehensive doctrine. The point is to be in Christ, and to approach Christ, and to live in Christ (and He in us).
Everybody should read a little theology. Some are called to devote their lives to it. But our call is to know and to be known. And, in the process and in the occasion, that's going to be messy. And I'm fine with that. A little anxiety and mess liven things up.
But it's that kind of acceptance of loose ends, that may be seen to be operative in the less than systematic approach Catholics take to Scripture and tradition. We see what looks to the "scientific" mind like a wild exegesis of the OT in Hebrews, the apparently malleable and plastic (not to say "Rubber") typological approach of the Fathers does not provide Newtonian or mathematical rigor. But it does exhibit hearts on fire. And when all the arguing about merit and grace and free-will and predestination is hushed, what we want is to be plunged into the living fire which burns but makes us whole. We certainly don't want to stand around on its edges vying with one another for the most precise and comprehensive description of it.
/rant off. I have to work today. SO I won't be able to follow this up too much.