Do Jesus’ words in Matthew 15 indicate that Scripture is superior to Tradition?

It is true that any proposed tradition that contradicts Scripture is a false tradition and must be rejected, but this does not make apostolic Tradition inferior to Scripture. It is also true that any proposed scripture which contradicts apostolic Tradition is a false scripture and must be rejected.

This was, in fact, one of the ways in which the canon of the New Testament was selected. Any scriptures which contained doctrines which were contrary to the Traditions the apostles had handed down to the Church Fathers were rejected.

From the Gnostic gospels (such as the Gospel of Thomas) and Marcion’s edited version of Luke’s Gospel and Paul’s epistles, there were a lot of heretical writings proposed by different groups for inclusion in the New Testament. But the Fathers said, “No, this contradicts the faith that was handed down to us from the apostles. Thus it must be a forged or otherwise non-inspired writing.”

So while a tradition must be tested against Scripture to see if the tradition is apostolic, it is also true that scripture must be tested against Tradition to see if the scripture is apostolic. There is complementarity here; one mode of teaching is not automatically inferior to the other.