hopefully the report system will discourage people from leaving without a good reason. That's toxic and selfish just like hacking, just not to the same degree. In the meantime just try and find some people, maybe through the Innersloth discord, that you can count on to play fair consistently, then add them as friends and invite them to a DM group. I did something similar, and it's been working out okay so far.
Basically, if the problem is that anyone can join, eliminate the factor that anyone can join. Easier said than done I know, but... ¯\_(ツ)_/¯