They're not designed for extended firefights, for taking out a biker gang, or for stopping a bank robbery by The Purple Gang.
Then from the article...
They are designed to be "shot little and carried often," not the other way around.
I always get a kick out of folks determining what a gun is "designed" to do. I have never seen design parameters on a firearm that state the length of firefight, activity to be stopped, etc. I have never seen one that stipulates how much it is or is not to be shot or carried.
As best as I can determined, "shot little and carried often" is a translation for cheap quality. Certainly, not all mouse guns are cheap quality. Such generalizations are misleading.
If you are under pressure, and are armed with a mousegun, you will do amazingly well to hit a man-sized target at three yards. Fast, excited shooting at over three yards is very iffy.
Either this applies to all guns in general or it is an issue of practice and training, not necessarily a shortcoming of the firearm itself.
Sights are rudimentary, and mouseguns are not tack drivers.
The military standard for a long time was simply being able to pattern 4" at 25 yards as being combat accurate for a pistol. The 1911 met this standard and it is NOT a tack driving standard at all.
Heck, point shooters don't even need the sights.
And here maybe we find the problem for why the author doesn't think people can hit a human-sized target at beyond 3 yards. Since they apparently aren't designed to be shot much and you aren't range guns, then owners won't practice with them.
----------
Maybe I missed it, but what is it about carry gun designs that make them more suited to be carried often? The only thing I could figure would be the lighter weight, but the lighter weight doesn't mean the guns are designed to be shot a lot. It just means they are lighter. Since the Kahr PM9 was mentioned in the article, I have over 7000 rounds through one of mine. It is light weight, is shot often, is used as a range gun for practice with sessions that often go over a couple hundred rounds and it is a fine gun for engaging targets at distances well beyond 3 yards. It would work well in an extended firefight (although few folks would have enough ammo on hand for such).
People often confuse the difference between design parameters and then end-user applications (intent). Just because something isn't designed for a certain parameter does not mean it won't be good for an end-user application. I think the author has confused several such points in the article.
It is sort of like with the whole "sniper" rifle concept. "Sniping" is a task application, often performed with a rifle designed to launch a projectile down range in a controlled manner with the precision needed to hit a target at distance (may be long distance). Whether that rifle is used for tin cans, bullseye matches, deer, or humans is all in the application, not the design. Designs may lend themselves to particular applications or may be what the designer had in mind, however.