It appears to me that the current state of Lemmy is similar to other platforms when they were smaller and more insular, and that insularity is somewhat protecting it.
I browse Lemmy, and it feels a bit like other platforms did back in 2009, before they became overwhelmed and enshitified.
If I understand it correctly, Lemmy has a similar “landed gentry” moderation scheme, where the first to create a community control it. This was easily exploited on other platforms, particularly in regards to astroturfing, censorship, and controlling a narrative.
If/when Lemmy starts to experience its own “eternal September”, what protections are in place to ensure we will not be overwhelmed and exploited?
What you’re worried about is basically what federation was built to stop.
If you don’t like the moderation of a community or other aspects, you or anyone else can make a new one on the same or a different instance, if you want.
You can even make it “private” (not federate) to keep others from coming in and recreating the problem you just fled.
To be optimistic, I’d hope the federation would be able to guard against deeper centralization like a more extreme .world or .ml, a la meta or whoever. There’s always space for grassroots instances, and I’m pretty sure there will always be someone out there running something or with enough interest to learn.