"All of that other stuff matters but what difference will any of it make if the gun doesn't go bang?"
Exactly.
"If you can't hit the broadside of a barn."
The majority of defensive shootings happen when the two individuals are within touching distance of each other.
At those distances, whether or not you can hit the broadside of a barn is really immaterial.
In all the years I've been involved with firearms, I've yet to meet an individual who couldn't reliably hit a mansized target - both hip and point shooting - at those distances, even some of whom have been pretty poor shots when the targets are backed off to 7 yards or more.
I know many of us tend to think along the lines that in a defensive situation we're going to need to draw an accurate bead over many yards, or we're going to need to be able to reload our handgun in less than 3 seconds so we can continue the fight.
Yes, it's good to practice for those things, but are they critical aspects of training?
Data says not.
Once again, the majority of defensive shootings happen within touching distance, or not much farther, and are resolved with fewer than three shots being fired.
That alone should tell us that we should be training to THOSE realities, not a fantasy where you're going to have to make a 71.968 yard shot, reload, and shoot again.
And, within the reality of those parameters, inherent ability to place 15 shots in COM of a B-27 at 10 yards, or slap a fresh 17-round magazine in your Glock in less than 2 seconds, get pushed far down the list of critical issues.
But, what does rise to the top?
Absolute firearm reliability.
If you're within touching distance of your assailant, you want that gun to be 100% reliable. You don't want to find out that your first shot to COM hasn't put the guy down, and now you have a dead gun in your hands and you have HIS hands around your neck. You want that gun to be reliable.
All else, in the reality of defensive shootings, is ancillary. An absolutely reliable firearm is most important.