I expect if you unfollowed everyone for it to show absolutely nothing, leaving a "consider following these people" prompt. And otherwise when I reach the end of new content, show me a "you reached the end of your unread content, consider following these people to add more".

Having a clear "you are caught up" point probably isn't positive for engagement metrics so I understand why they don't do it but I'd rather the app be oriented towards UX than to be oriented towards engagement metrics.