I understand you. Read Galatians 1:1-10. And Revelation 22:18-19. If someone tells me something from the Bible, the must show me where I can read it. If someone says to me the Trinity God or triune god, I will see it written in the Bible. If someone tell me God Father God Son and God Holy Spirit. I will read it in the Bible. Do you understand me now? I belief what is written in the Bible. Not man teachings, but Jesus and the apostles teachings.
Yes I understand that you believe what is written in the Bible, no more or less. And yes, I accept scriptures other than the Bible. I understand why my appeal to those other scriptures would not impress you. But my point is that there are millions (or billions) of Christians who would say with complete sincerity exactly what you said above. Yet they would disagree on points of doctrine because they read the exact same scripture differently. A conversation among such Christians could go like this:
Christian 1: "Doctrine x is plainly taught in this verse."
Christian 2: "No that is not what that verse means."
Christian 1: "Yes it is what God means. He said it right there in the verse."
Christian 2: "I'm sorry friend, but God said the scriptures are not for personal interpretation. I believe only what God says".
Christian 1: "I am not personally interpreting the scriptures. I'm just reading what God said. Why do you not believe what God says?"
Christian 2: "Satan has decieved you into believing that which is not written."
Christian 1: "No my friend, you are misinterpreting that which God plainly said in this verse. Shame on you for your personal interpretation."
My theory is that neither Christian 1 or Christian 2 likes to admit to this, as they think it weakens the Bible. It implies the Bible does not interpret itself and it's teachings are not always self evident. That begs the question of why God would leave us in a tentative position with ambiguity. Those are hard questions to answer for Christians who believe what you said above.