By that definition, not only sola Scriptura but other Christian doctrines, as well as those specific to Catholicism or Reformation theology are superstitions. Original sin, the Immaculate Conception, and the the priesthood of the believer are as superstitious as sola Scriptura, For that matter, so are doctrines found in all religions.
The point is, Sola Scripture proclaims that no truth important to faith formation is to be found outside of the scripture. If that were true, then Sola Scriptura would be itself a doctrine found in the scripture, but it is not, -- no basis in fact.
On the other handm the "faith once delivered to the saints" is a historical fact undergirding the Holy Apostolic Tradition.