The error that you make is that Protestant thought is the arbiter of God. Scripture is a testimony of God, and is not God Himself. If you limit God strictly to scriptures, you commit the error of the Pharisees in John 5.
39- Search the scriptures, for you think in them to have life everlasting; and the same are they that give testimony of me
40 And you will not come to me that you may have life.
41 I receive glory not from men.
42 But I know you, that you have not the love of God in you.
43 I am come in the name of my Father, and you receive me not: if another shall come in his own name, him you will receive.
44 How can you believe, who receive glory one from another: and the glory which is from God alone, you do not seek?
Christ Himself does not limit God to the scriptures. Christ is a person, not a book. Scripture is a testimony, not a person.
Scripture itself in Paul’s letter to Timothy does not say that scripture is all there is. It says the Church is the pillar and foundation of truth.
Christ laments Jerusalem, He does not say oh Jerusalem, you who did not read the book. No!
He cries Jerusalem, you who slew the prophets
God sends people not books.
If we limit God to a book, we lose everything else God has given us. Scriptures says he gave some Apostles, some prophets, some evangelists, some pastors and teachers. These are people , not books. If we ignore the people sent to us, how can we claim to believe the book written about them?
Even the Bereans, so often used in support of scripture only, merely used the scriptures to validate Paul as an Apostle, they did not use scripture to discard Paul and go off on their own
Scriptures testify of Jesus and His Church. There is no justification to use them to discard the people that God has sent to us