The irony is that many unbelievers have taken it upon themselves not only to alter the fundamental text of the Bible (thus making things with apocryphal additions such as found in the Vulgate or DRB), but also to try to claim to have originated the Scripture itself, declining to even give God the glory for writing his own word. I have had discussions where some Orthodoxes would insist that, what they call the church (actually the state church) CREATED the Bible. That is to say, Not God. They would argue me on that point, saying it was actually them that created the Bible rather than God being the author.
You can see how ironic it is that we don't use the same version as them at the same time as they claim this.
>to establish the biblical canon
To this I would again say, Thy word is true from the beginning: and every one of thy righteous judgments endureth for ever.
When we read that the word of God was "spreading" in the book of Acts, that tells us that His word was already fixed and immovable (Matthew 24:35), just as God inspired His word and gave and confirmed the word by His Son (Hebrews 1:1-2) and by the Apostles (John 17:8, 2 Peter 1:21). This means that no council or group truly determined God's word. But rather, by the determinate counsel of God, His word has been true from the beginning, and revealed (Galatians 1:12, Titus 1:3, Deuteronomy 29:29) in due time according to the will of God. (Daniel 12:8-9, Revelation 22:10).
Thus His word has been true and self-evident from the beginning. Hence the Lord Jesus Christ tells the Pharisees & scribes, in John 8:47 that, "He that is of God heareth God's words: ye therefore hear them not, because ye are not of God."
The inspired prophecy obviously did not magically become true only when someone arranged their contents in a single physical tome. Rather, the words of prophecy have always been true and God providentially preserves them to every generation (Matthew 24:35, Psalm 12:6-7, Proverbs 30:5, Isaiah 40:8, 1 Peter 1:23-25).
>As it is their beliefs are based on the supposed interpretation of church tradition through the bishops and the Pope, with all its subjectivity.
And this part is just as much rebuked by Christ in Mark 7:7-13. The non-Biblical traditionalists stand rebuked by the truth here. They lay aside the commandment of God to turn to traditions of men. This is absolute, rebuking not only the Pharisees of Christ's day, but modern-day equivalents in all the manmade traditions of today which are just as fake as the Pharisaic "oral tradition" that Christ rebuked.