I do not agree
That's your right. Consider, though, the question of authority. The Epistles were written to the Churches to build up their faith and correct what was flagging. By what authority would these be written to multiple churches if they were not from the authority of One common Church? One common Faith?
For example... would a Baptist authority be respected in a Catholic Church or vice versa? No. There was One Faith, One Body, One Church united under One Christ Who is building up His Bride. Feel free to disagree but your disagreement isn't ultimately with me.
“I do not agree”
Care to share how the Corinthian Church differed in doctrine from the Roman or Jerusalem Church?