There are a lot of communities that were created in the last week but never had any kind of interaction or their mods never started to post to attract people (they don't even have rules or a description).
Will there be some kind of cleanup or will it stay there until someone asks to take over it?
I think it's reasonable to get rid of empty/inactive communities after x period of time. Other instances do something similar e.g. https://lemmy.dbzer0.com/post/56147
There are also other instances that sidestep the issue entirely by disabling the ability to create communities on that instance.
An empty community, or one that only ever had a few posts & then kind of died out, probably isn't worth keeping around IMO. But I also think that could be decided on a case-by-case basis by the instance admins.