A point I bring up often when forum members discuss home defense rifles/shotguns is a good video on www.youtube.com
a quick thinking crook can disarm a home owner/tenant holding a rifle-shotgun.
need to be a Ninja or SEAL to do it either.
As noted, with a long gun, you are operating in close quarters(CQB). Retention & good tactics are required. Having a free hand(or two free hands with a holstered firearm) may be necessary.
The point about shotgun slings is good. Denny Chalker, a retired US Navy SEAL who served on the elite SEAL-06 & Red Cell
counter-terrorist unit invented a sling attachment that allows a weapon to be quickly detached. The rig became very popular with SWAT units & spec ops who worked in CQB situations. I'm not sure what site or company markets it but it's not a bad idea.