I mentioned the issues with Chess sites trying to rank bots, but I'd find it even harder to sort out for cooperative games when you add in things like teamwork considerations. Having certain players basically carry the game while others reap the rewards can be a real thing for some games. I'd consider have the ratings affected by who the teammates were, the stronger your teammates are, the less you should gain.
There are several ceiling issues, the commonly referenced boosting, but also the lack of a proper challenge ceiling in some cases. If all of the challenges are easy enough everyone's compared rating is how they just forever grind the wins for lack of something to really filter them. Artificial challenges do lack the natural balancing factor competitive games have as players will throw each other's ideas back and them and continue to refine them.
There are several ceiling issues, the commonly referenced boosting, but also the lack of a proper challenge ceiling in some cases. If all of the challenges are easy enough everyone's compared rating is how they just forever grind the wins for lack of something to really filter them. Artificial challenges do lack the natural balancing factor competitive games have as players will throw each other's ideas back and them and continue to refine them.