The primary limitation of the shotgun is length. In close quarters even the 18.5 inch barrels can become difficult to maneuver.
The other misconception is the pattern of the shot. In close quarters it does not have time to spread. Therefore, it is just as easy to miss as hit.
Perception is another problem. Many people think you can pick up a shotgun, without practice and training, and immediately take out a target. My own experience indicates that you must practice. Granted it takes less practice to become proficient with a self defense shotgun than a pistol.
Even an experienced shot gunner cannot pick up a new weapon and expect to perform satisfactorily.
I have used shotguns most of my life. I am proficient on rabbit and squirrel. Yet, when I purchased my Mossberg short barreled shotgun with collapsible stock, I went to my range. At 10 yds. I engaged three standard targets in rapid succession. I missed all three targets. I then engaged the same targets with my Rem 1100. I hit each target in the 10 ring. It took several sessions to obtain a minimal proficiency