For me its having a single instance that indexes all the communites to which all other instances can then pull that information from so when I go searching for communities the I’ll have access to every single one with needing to post the entire URL in the search bar
I would love to have tags added that I could search at across instances. So looking up #animalpics might be all the communities that post pictures of animals
Then add to that the ability to follow that tag like you can on Mastadon and that would solve some of the “Super Community” asks.