Bible study 101:
What is the context of these "traditions" Paul is writing about?
St. John Henry Newman explained it in an 1884 essay entitled Inspiration in its Relation to Revelation. Newmans argument
He wrote: It is quite evident that this passage furnishes no argument whatever that the sacred Scripture, without Tradition, is the sole rule of faith; for, although sacred Scripture is profitable for these four ends, still it is not said to be sufficient. The Apostle [Paul] requires the aid of Tradition (2 Thess. 2:15). Moreover, the Apostle here refers to the scriptures which Timothy was taught in his infancy.
Now, a good part of the New Testament was not written in his boyhood: Some of the Catholic epistles were not written even when Paul wrote this, and none of the books of the New Testament were then placed on the canon of the Scripture books. He refers, then, to the scriptures of the Old Testament, and, if the argument from this passage proved anything, it would prove too much, viz., that the scriptures of the New Testament were not necessary for a rule of faith.