F2P games are by far the worst. I dont really know what the solution is but ive stopped playing more than a few games due to the MP becoming to toxic and the devs failing to do anything effective about it.
To review, it's not clear what can be done. No moderation leads to lots of bad behavior, automated punishment leads to reporting abuse, and moderated punishment is impractically expensive. One idea is some sort of player volunteer trusted moderation.