Like the revolver and the lever-action carbine, the shotgun is still around because it gets the job done and gets it done quite well.
You can say what you want to about your favorite defensive school or those advanced-fighting techniques you learned, but the greatest defensive skill that a person can develop is simply awareness. I will freely admit that developing effective awareness is anything but simple, but being able to spot trouble before it is close enough to get in your face will certainly save you from a lot of trouble and possibly even some pain and grief.
Training with and relying on a partner can be a pivotal element of any personal defense preparedness.
When we can, we need to tell the new shooter that they really need to learn to walk before they can run. And then we need to help them find the kind of training that will give them the basics of safe gun handling and marksmanship.
What is a suitable quick-draw time, and how important is that for the armed defense with a handgun?