Catholics agree in what is called the "material sufficiency of Scripture." Or, as it's sometimes phrased, that the Bible contains all revealed Truth, either explicitly or implicitly. We just disagree that the Scriptures are formally sufficient, in that a) reason and experience demonstrate that the Bible is not self-interpreting, b) the Bible demonstrates there is a church granted teaching authority, and c) the Bible warns about divisions in teaching and understanding.
So the Bible is materially sufficient and formally insufficient.
Based on what? When and where was that decision reached and who decided that and why?