That people have been making the same mistake for millenia doesn't mean that it isn't a mistake.
I like to remind those who say "Paul wrote..." when discussing Scripture that;
"All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the man of God may be thoroughly equipped for every good work.", 2 Timothy 3:15-17
It's quite a common mistake, even among learned theologians.
Noting that St Paul did not preach from written gospels and that Timothy was eduated by word of mouth from his Grandmother.
The reason scripture was written was to stop the gnostics from perverting it NOT to represent the whole of Christian theology.