I think there needs to be some love shown for competitive games as well. When you are playing some games with friends that are honest and don’t cheat competitive PvP is a ton of fun - especially when you can make up your own additional rules like “Cops V Robbers” play as children. Problem is this can only be had on private servers with friends or people you have come to know online and can trust within the game space.
One place to start I think is asking how does the game scale when another player comes with you? Is the game experience easier, or different. Obviously WOW raids were built for coop, and the benefits of such are greater than solo play. I know right now they are working on 7 Days to Die scaling differently as far as number of zombies based on the collection of players in proximity and their levels.
I think some games like Minecraft do have a “natural scaling” aspect to them and so are more subtle within the design - where as a team you can build something better than alone, because time to task is a component. “I will build the road while you work on the bus stop”.