But of course. A superstition is a metaphysical belief not supported by observable fact. Sola Scriptura qualifies.
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.