I think anyone on a desert island is already ahead of the game in regards to primitive survival skills as a hedge against apocalypses. The only thing that they would need to overcome is their own environment (food, water, shelter). In an apocalypse you have to overcome their own environment plus their neighbors. Change the desert island to a neighborhood and 9/10 Dentists would pick the rifle.
Sadly, you've ignored that survival without society is the root problem. Yeah the island might protect u from zombies and other people, but u got abt 3 days to get potable water regardless of what's happening on the mainland.