The AR-15 derivated guns in 5.56mm tend to be decently mechanically accurate (depending on the exactly setup and blahblahblah) and have a flat trajectory which makes them practically accurate.

The ability of 5.56mm to wound is velocity dependent. Within the range where the velocity is high enough (600 to 800 meters, again depending on specifics) they are quite damaging, at least to humans. 5.56mm was designed specifically with humans as targets in mind, and designed to kill with hit to the heart/lungs/head. It minimizes recoil to allow the maximum volume of aimed shots in the shortest time, to maximize the chance of hitting a vital.

For hunting something like deer, a lot of gun people have shown 5.56mm is capable of taking down a deer with a similar hit to the vitals, however many locations still regulate that 5.56mm is not legally allowed, so it’s sort of a moot point.

For home protection I would want a pump action 12 gauge.

Not my personal choice or recommendation, but I’ve had this conversation enough to know it is hard to change minds.