Following the announcement by beehaw admins to defederate from lemmy.world and sh.itjust.works, there has been many posts and messages regarding that decisions and what other instances will do.
I personally believe Lemmy/kbin can only thrive if there is a free flow of content between different instances, with instance admins taking a back seat and focusing more on the infrastructure and making sure the technical bugs are smoothened out. Community mods can moderate their communities, and users can block the communities they don't find appealing (there's even a toggle in settings to hide every NSFW post from your feed altogether).
We don't want to create walled gardens, nor do we want to make Lemmy more confusing than it already is for new users. We will not be defederating from any instance if there is even one good community on it that our instance users might find useful. So far we have only blocked lemmygrad.ml, and right now we have no plans to block anyone else.
The problem at the moment is that the community moderation tools are pretty limited. At some point there will be coordinated attacks on some communities and the moderation tools are not yet sufficient to defend against that sort of thing.