“...not much of an argument against Sola Scriptura...”
Sola Scriptura is a manmade doctine. The canon of the bible is not found within the bible or listed within the bible so it is extrabiblical.
The following words and terms are not found in the Bible either so they must be, according to your criteria, also of necessity be extra-Biblical. And yet the Catholic church teaches them as truth.
trinity
catholic
pope
eucharist
sacraments
annulment
assumption
immaculate conception
mass
purgatory
magisterium
infallible
confirmation
crucifix
rosary
mortal sin
venial sin
perpetual virginity
apostolic succession
indulgences
hyperdulia
catechism
real presence
transubstantiation
liturgy
free will
Funny that......