“Moreover, they possess no proof of their system, which has but recently been invented by them...Such, then, is their system, which neither the prophets announced, nor the Lord taught, nor the apostles delivered, but of which they boast that beyond all others they have a perfect knowledge. They gather their views from other sources than the Scriptures...” (Irenaeus)
Nothing “secret” in that quote. It simply states that the Gnostics uses sources not contained in the Scriptures.
The Catholic position is this: “We assert that the whole necessary doctrine either concerning faith or manners is not contained explicitly in the Scriptures; and that consequently beyond the written word of God is required also the unwritten word of God, that is, the divine and apostolical traditions...” (Robert Bellarmine after the council of Trent)
Then here is what Irenaeus said on the subject.
“Since, therefore, the tradition from the apostles does thus exist in the Church, and is permanent among us, let us revert to the Scriptural proof furnished by those apostles who did also write the Gospel, in which they recorded the doctrine regarding God, pointing out that our Lord Jesus Christ is the truth, and that no lie is in Him.” (Irenaeus)
“We have learned from none others the plan of our salvation, than from those through whom the Gospel has come down to us, which they did at one time proclaim in public, and, at a later period, by the will of God, handed down to us in the Scriptures, to be the ground and pillar of our faith.” (Irenaeus)
It couldn’t be any clearer. If it isn’t in the scripture we should not trust it. So stop with the “oral tradition” which early Church fathers clearly stated were then written down in the scriptures. It plainly states that what they had orally “proclaimed in public” was written down in scripture.
I don’t think it’s prudent to base the totality of your knowledge on Gnosticism on a few paragraphs attributed to Ireneaus. Also, as great as he may be, he is not the sum total of thought regarding Sacred Tradition, the Church and the early church Fathers.