Public revelation ceased with the death of the last Apostle. But these discussions always ignore the fact that the Bible (written revelation) is not the only source available to us from Apostolic times. There's also the preaching (oral teaching) of the Apostles and the lived practice of the Apostles. St. Paul says to pay attention to this.
2 Thessalonians 2:15
traditions which ye have been taught, whether by word, or our epistle.
2 Thessalonians 3:6-9
And we charge you, brethren, in the name of our Lord Jesus Christ, that you withdraw yourselves from every brother walking disorderly, and not according to the tradition which they have received of us.
For yourselves know how you ought to imitate us: for we were not disorderly among you;
Neither did we eat any man's bread for nothing, but in labour and in toil we worked night and day, lest we should be chargeable to any of you.
Not as if we had not power: but that we might give ourselves a pattern unto you, to imitate us.
We are to learn from their words (preaching), their writings (epistles) and their example (we imitate their conduct.)
That's why it seems so unsatisfactory to dismiss some teaching because "Well, that isn't in the Bible." It still part of what the Apostles taught, which is why it is authoritative.
And how do we know it;s what the APostles taught? Becuase it's what was handed on, taught and practiced in all the churches founded by the Aposles. In the churches of northern Africa, Mediterranean Europe, and the Middle East.
All that can be irrelevant, only if the church is irrelevant.
What is the pillar and foundation of the truth?
“We are to learn from their words (preaching), their writings (epistles...”
If so, it appears in Scripture.
Your follow up point is again an argument from silence - simply an assumption that what we have today is what was seen or heard and passed on. Nothing but an assumption that an unbroken chain occurred.
It did not. Nor can the first link before 100ad be verified.
And much that your denomination classifies as tradition was added hundreds of years later. Ratzinger himself, in his writings, makes this clear.
Which brings the believer back to God’s Word as the authoritative source of inspired truth. It cannot be added to, not taken away from to create new teachings or add strange fire.
Best