mods basically ruling over them
A proper mod isn't a ruler, but rather a janitor - someone who keeps the place clean so others can enjoy it. Without that, it is only a matter of time until someone decides to shit all over the place for funsies and then you can either decide to clean up - at which point you become a mod - or continue hosting the shitshow, and that is never fun. I don't know about a single "anarchist" social media site that lasted longer than a week at best, so I doubt it is possible.
Imagine you actually hosted a completely anarchist site and then you start to recieve death threats, doxxing, literally illegal content etc. .. what are you going to do then? Serious question.