As a Catholic, I believe that “sola scriptura” is wrong. Scripture is not sufficient by itself as a rule of Christian faith. It’s obviously wrong, too, because Scripture cannot say what counts as Scripture or not. So the Church is necessary too.
But perhaps you have tended to think of this matter along these lines: there are many things we need to believe as Christians, which are only implicit, or not even clearly stated, in Scripture. Baptism is the crucial sacrament of salvation. But infant baptism is taught only implicitly: babies presumably were baptized when households were. (see Acts 10:48) As for the foundational doctrine of the Trinity: it is simply not clearly stated in Scripture, or even in the early Fathers, as Newman never tired of pointing out. That’s why the Council of Nicea was necessary.
On this view, the Church is necessary as adding something that Scripture does not explicitly or clearly say. …