I think you're basically right. The 9/11 hijackers had valid, government issued ID.
Yet somehow there are people that are convinced that showing that ID to government agent magically makes the flight "safer."
Well, you showed ID? Must not be a hijacker then. All right, onto the plane with you. Very good. No problem here.
Twenty years ago I briefly worked as a bouncer and I could pick out the potential trouble makers better than our TSA can pick out potential terrorists and the bar I worked at had 99% white American customers. I didn't have the benefit of skin color, accent or ethnicity as a clue.
BTW, the trouble was never with the 1% non white customer. It was always those white guys who all looked alike, but I knew enough about people to see who was gonna be trouble and who wasn't.
People skills and common sense would go a long way with airline screening, but those seem to be the two things that aren't required.