The Tuck Rule

The entire process takes only a second. You are assuming that at some point in that second the QB changed his mind from attempting a throw to not attempting a throw.

The rule says that when the ball is against his body, the throwing motion has ended.

If you don't want the Tuck Rule, then you are saying that you'd rather the referee read the QB's mind about at what point his intention changed. Good luck with that.
But the ref didn't see it- that's why they had the replay. They required replay evidence to show McNair was attempting to tuck the ball away, not to throw it, and the current rule says that is an incomplete foward pass. We aren't asking for psychic refs, just common sense. Right now, a botched pump fake is an incomplete pass. The pass should start with foward motion, but to require the ball to be completely tucked in for the attempt to end is just wrong.