You would be adult saying “yeah, Benny, but everything with friends is fun. I don’t think throwing stones into river is good fun”.
My point being: even worst games can be fun with friends. Take out friends, what you are left with: poop-quality game.
That’s the problem of many failed co-op games. People are on copium as long as they have people to play with. Hell, even Battlefail 2042, being total big pile of dog shite was fun with my friends for some time (still, I heavy criticized this game, as it was 3/10 at best, dog shait).
So that doesn’t mean that game is fun, just that I like to spend time with my friends and they make my time fun, derping together.