Scripture seems to be very important, necessary in fact, from an early church standpoint, in establishing and confirming doctrine:
“They that are ready to spend their time in the best things will not give over seeking for truth until they have found the demonstration from the Scriptures themselves,” - St Clement of Alexandria
“No man ought, for the confirmation of doctrines, to use books which are not canonized Scriptures,” - Origen
“The Holy Scriptures, given by inspiration of God, are of themselves sufficient toward the discovery of truth…The Catholic Christians will neither speak nor endure to hear anything in religion that is a stranger to Scripture; it being an evil heart of immodesty to speak those things which are not written,” St Athanasius
“How can we use those things which we do not find in the Holy Scriptures?” - St Ambrose
“Not even the least of the divine and holy mysteries of the faith ought to be handed down without the divine Scriptures. Do not simply give faith to me speaking these things to you except you have the proof of what I say from the divine Scriptures. For the security and preservation of our faith are not supported by ingenuity of speech, but by the proofs of the divine Scriptures,” - St Cyril of Jerusalem
“Those things which they make and find, as it were, by apostolical tradition, without the authority and testimony of Scripture, the word of God smites… As we deny not those things that are written, so we refuse those things that are not written." - St Jerome
Now, this establishes the great importance of the Scriptures. At least, there is a material sufficiency of scripture, Catholic apologists would say.
In this case, however, where can we actually find something like the Assumption of Mary in scripture? Having a pious belief in Mary’s assumption is one thing, but to have it actually proclaimed as dogma, actually defined as an article of faith for all Catholics? Does this not defy St Cyril’s ruling that “Not even the least of the divine and holy mysteries of the faith ought to be handed down without the divine Scriptures”? If it does defy this rule of St Cyril’s, what is to be said of the inerrancy of papal proclamations? Ecumenical councils in the early church took decades, heck sometimes even centuries to be fully recognised as ecumenical, they weren’t recognised as ecumenical the moment the Pope gave his approval. So when the Pope proclaims a dogma without the use of the Scriptures, do we just take it on faith, do we ignore the teachings of the church fathers? What use are the church fathers then, were many of them wrong about their beliefs about scripture? Are scripture and tradition just two sides of the same coin, or do the church fathers’ teaching show that scripture is a bit more than just that?
I have heard the response that the Woman in Revelation is Mary and this somehow shows her Assumption? Does anyone honestly find that convincing though? How can one reconcile the Assumption of Mary with many of the church fathers’ teaching that doctrine should be taught with scripture, that “Those things which they make and find, as it were, by apostolical tradition, without the authority and testimony of Scripture, the word of God smites"?