Well, you are basically saying that you know which tradition is "legit" because the Roman Catholic Church said so!
The Protestants reevaluated some of these "traditions" and checked them against the scriptures and from there ditched many of them. Most of these so-called "traditions" evolved over the years and were completely non-existent during the apostolic era - especially those pertaining to Mary's immaculate conception, assumption, and so forth.
Baptists admittedly have their own traditions that creep in such as 10AM Sunday School, 11AM Main Service, singing out of a hymnal and always skipping the second to last stanza, etc. Some of these traditions can become quite "Sacred" to certain Baptists especially if you are found sitting in their seat!
The books that make up the Bible were received by the Church. I have already stated that we have two completely different views pertaining to what the Church is but needless to say, it was not a bunch of bishops and cardinals sitting in a room sorting out what books did and what books did not belong in the canon. The church instinctively knew which were authentic, which were not, and which were inspired and canonical and this happened over the course of time. When someone actually compiled the 27 books of the NT, they were simply acknowledging what the church had already received. Nothing more, nothing less. The content of the Apocrypha was always debated among the Jews as well as the Christians and even today, they (Roman Catholics, Eastern Orthodox, etc.) cannot agree on which books of the apocrypha are canononical or should be included.
The Roman Catholic Church as we know it today did not exist during apostolic times. It evolved into what it is over the centuries - especially during the medieval era.
The Catholic Church did exist in Apostolic times otherwise it would not have been able to canonise the Bible scriptures.
All 73 books of Scripture in 382 ad. The Council of Rome. By Pope Damasus
“Likewise it has been said: Now indeed we must treat of the divine Scriptures, what the universal Catholic Church accepts and what she ought to shun. The order of the Old Testament begins here: Genesis one book, Exodus one book, Leviticus one book, Numbers one book, Deuteronomy one book, Josue Nave one book, Judges one book, Ruth one book, Kings four books, Paralipomenon two books, Psalms one book, Solomon three books, Proverbs one book, Ecclesiastes one book, Canticle of Canticles one book, likewise Wisdom one book, Ecclesiasticus one book. Likewise the order of the Prophets. Isaias one book, Jeremias one book,with Ginoth, that is, with his lamentations, Ezechiel one book,Daniel one book, Osee one book, Micheas one book, Joel one book, Abdias one book, Jonas one book, Nahum one book, Habacuc one book, Sophonias one book, Aggeus one book, Zacharias one book, Malachias one book. Likewise the order of the histories. Job one book, Tobias one book, Esdras two books, Esther one book, Judith one book, Machabees two books. Likewise the order of the writings of the New and eternal Testament, which only the holy and Catholic Church supports. Of the Gospels, according to Matthew one book, according to Mark one book, according to Luke one book, according to John one book. The Epistles of Paul [the apostle] in number fourteen. To the Romans one, to the Corinthians two, to the Ephesians one, to the Thessalonians two, to the Galatians one, to the Philippians one, to the Colossians one, to Timothy two, to Titus one, to Philemon one, to the Hebrews one. Likewise the Apocalypse of John, one book. And the Acts of the Apostles one book. Likewise the canonical epistles in number seven. Of Peter the Apostle two epistles, of James the Apostle one epistle, of John the Apostle one epistle, of another John, the presbyter, two epistles, of Jude the Zealut, the Apostle one epistle.” Pope Damasus (regn. A.D. 366-384), Decree of the Council of Rome, The Canon of Scripture (A.D. 382).
Catholics had the scriptures because they are the Apostolic Church.