I played World of Warcraft and other MMORPGs for years it was fun but co-op(like 4-8 players max) and single player games always was more fun to me.
NPCs unlike other players doesnt ruin gaming experience,lore and whole universe. In single player games you clicking start game and u already playing,doenst matter how bad is your gear and how bad is your gaming experience you having fun.
In mmorpgs its not like that you have level up,spent hours grinding gear and money for getting best gear before you actually will start having fun.