Even though the church did use various means to determine who wrote them that knowledge in and of itself does not make the NT inspired nor does it count against sola scriptura.
Just because a “tradition” about something may have been used to help to determine who wrote a particular book does not mean all traditions of the catholic church are right and sola scriptura is false.
The case for the inspiration-imerrancy of the Scriptures is well established. Both catholics and protestants accept this for the most part. What catholics need to show is that their “traditions” are on the same level as the Scriptures. That has yet to be shown. In fact i personally have yet to see a list of all the traditons of the catholic church. I wonder if such a list exists.
A PARTIAL List of Catholic Traditions
Baptismal Regeneration
Apostolic Succession
The three-fold ministry (Bishop, Priest, Deacon)
Sacrificial Nature of the Eucharist
The Substantial Presence of Christ’s Body, Blood, Soul & Divinity in the Eucharist
The Primacy of the Bishop of Rome in Succession of the Petrine Ministry
The Authority of Tradition and the Magisterium
The Infallibility of the Teaching Church
The Canon of the OT and NT
Sunday as the day of worship
Purgatory
The Immaculate Conception
The Perpetual Virginity of Mary
The Assumption of Mary
All public revelation ended with the death of the last Apostle.
Private revelation is not binding upon the faithful.
Communion of the saints
The permanent character of baptism
Sacrament of Confirmation as indelible upon the soul
Sacrament of Holy Orders as indelible upon the soul
Infused Grace
The Hypostatic Union
Knights of Columbus Spaghetti Dinners
Bingo