Zuriel gets at the heart of the concern. The apostles were specifically ordained by Jesus, and of course Jesus we trust. But we were specifically taught to look out for false teachers.
As the demon said to the seven sons of Sceva when they attempted to exorcise him:
“And the evil spirit answered and said, Jesus I know, and Paul I know; but who are ye?” Acts 19:15
I trust the Scriptures written by the designated apostles. I trust the Old Testament that was quoted by Jesus as authoritative. Men who teach who are not apostles are subject to scrutiny of Scripture by me. If they teach doctrine contrary to Scripture or in addition to Scripture, I reject it. I have to. Jesus said to watch out for false teachers.
Persevero:
So my question to you is which, among the thousands of Protestant Sects is the most representative expression of orthodox Christian Doctrine?