...but if you rely on it as a method of "gunfight" training, it is going to get you killed.
I hear that so often, but I still fail to see how practical that sentiment really is. Is anyone going to actually hear that "bump in the night" and think, "I'd better run out and engage a bunch of targets just like I did in the walkthrough?" Or expect to stand there on a dot and shoot mozambiques just like in the Classifier, when a seriously bad dude is presenting a lethal threat?
IF we were mechanical robots responding only to the programming written in during IDPA, USPSA, PPC, or whatever, that would be true. But I don't believe humans really work exactly like that. I don't think IDPA is writing in programming that will get anyone killed.
Rather, I see IDPA as writing in programming that can improve some of the intermediate-level shooting tasks that you might be called on to perform in a defensive situation. There are areas of defensive strategy where there are holes in that programming. Where an "IDPA education" is going to leave the practitioner to fill in the gaps in that programming as best as they can.
By the same token, though, you could look at Gunsite's 150 level or even 250 level defensive pistol classes and say the same thing -- if you address your gunfight through rote manipulation of these processes, it's going to get you killed. The education isn't complete. It may or may not adequately prepare you for the fight you really will have. You're going to have to fill in the holes as best as you can when your threat presents itself in its own unique way.
Whatever level of training and practice you have will prepare you to do things better than you would have otherwise. That may or may not be good "enough." More complete training will prepare you for a higher degree of complexity in engagements.
Fortunately, though, a great many defensive encounters are settled without a shot even being fired. And when a shot IS fired, a great many defensive encounters are positively concluded even though significant tactical mistakes were made by the defender. Each higher level of training (and practice) we avail ourselves of should reduce the number of mistakes we're likely to make in addressing a threat -- and the only reason higher levels of training exist is that some things presented at lower levels of training, if taken as rote, will "get you killed."