St. Peter tells us that we must be taught what Scripture means, or else possibly suffer destruction (2 Peter 3:16)
Also, you have to understand the difference between formal sufficiency of Scripture and material sufficiency of Scripture.
The Bible, with or without the Deuterocanonicals, is materially sufficient. That means that everything we need is in there, but we probably won’t be able to find it because we wouldn’t understand without Tradition, without knowing what we were looking for.
Formal sufficiency means that everything we need would be in there and we have all we need to find and understand it. This is what Protestants believe.