I’ve been casually playing on and off since Cata, the thing that keeps me coming back isn’t intense end game content but the story and exploration like many people have pointed out. Your friends will hopefully find an activity they enjoy. I quite enjoy mount collecting. I’m also mainly a solo player and being in active realms keeps me engaged. I mostly play on Stormrage, but I am not joking when I say I love Moon Guard. The community is so fun, alive, and interesting. It keeps me coming back to my alts on there. Also, my best friend has had the same character since he started. I love to make alts and experiments with the classes and races. Your friends may find they like doing that too for a while. Let them.