To my understanding, the restoration of old boards/"maek nuu boreds plz!!!" has been a topic for about as long as Kaguya has been admin. The answer I always see that usually ends the discussion is something like this: we can't add new boards at the moment because the userbase is so small that new boards would only divert attention away from our current boards and therefore cause the activity to stagnate.

Don't take my word for it though, I'm sure a mod or Kaguya himself can vouch for that claim or correct it. There are some old threads and archives of more threads lying around somewhere but I'm too lazy to find them at the moment. ¯\_(ツ)_/¯

Oh and /f/ is technically still around (img.heyuri.net/f/), but it's a ghost town. Only two new posts have been made there in the last two weeks.