I did a search from shitjustworks for “reddit die” and did not find https://lemmy.world/c/watchredditdie so I made https://sh.itjust.works/c/watchredditdie (unnecessarily). This should really not happen. When someone makes a community there should be a “ping” sent out to notify all other federated instances.
And from what I know, if I post to !sh.itjust.works/c/watchredditdie only users on sh.itjust.works will see the posts until other people from other instances randomly come across it somehow and subscribe? This really needs to be improved.
But your solution would require every new instance to subscribe to every community in existence even if no users there care about certain ones. It’s innefficient.
How would you know no one cares if no one can even see them…
“Inefficient” doesn’t seem important since if there’s no content/activity there then it doesn’t use any resources.