First I have a question for you, and respectfully, please answer this at the BEGINNING OF YOUR REPLY. Please.
Did Peter and Paul make any mistakes in their ministry at ANY TIME? Did Messiah make any mistakes? Who is the prophet WE MUST HEAR AND OBEY?
Why no talk of if I accept John, Peter, Jude, James, etc? And was Paul's letter to a particular group to every other group? Yes they can all learn from his writings but they were tailored to SPECIFIC groups of people WITH SPECIFIC ISSUES, issues we DO NOT FULLY UNDERSTAND.
MOST IMPORTANTLY, if you want to claim a doctrine out of the mouth of ONE man and it is not in the mouth of 2 or 3 not that the Scrip is wrong, but the interpretation may be wrong.
Who is singled out as hard to understand? And it just so happens that people isolate this writer that is hard to understand and build doctrines without considering other Scripture. So the error is not in Paul but in people's understanding.
2 Kepha 3:15-16, "...Shaul, in accordance with the wisdom given to him, has written to you, As also in all his letters, speaking in them about these things, in which are some things hard to be understood, which those who are unlearned and unstable twist, as they also do the other Scriptures, to their own destruction."
This was written for a reason to ignore it is folly.
With that said All Scripture is profitable, but must be looked at as a whole IMO.
However there is only ONE who Yahweh said we must shamaw.
John (Yahchanan) 14:6, "Yahshua proclaimed to him: I am the way, the truth, and the life; no man comes to the Father, except through Me."
Luke 6:46, "And why call Me; Ruler! Ruler! and do not the things which I say?"
Yahchanan (John) 4:25-26, "The woman said to Him; I know that the Messiah comes, and when He comes, He will tell us all things. Yahshua said to her: I am He speaking to you."
Deuteronomy 18:18-19, "I will raise up for them a Prophet like you from among their brothers, and I will put My words in His mouth, and He will tell them everything I command Him. Whoever will not listen to My words, which He speaks in My Name, I will judge him for it"
"listen" is word #8085 שָׁמַע shama` {shaw-mah'}
Brown-Driver-Briggs (Old Testament Hebrew-English Lexicon)
A primitive root; to hear intelligently (often with implication of attention, obedience, etc.; causatively to tell, etc.)
Hebrew Word Study (Transliteration-Pronunciation Etymology & Grammar) - 1) to hear, listen to, obey