With Meta starting to actually implement ActivityPub, I think it would be a good idea to remind everyone of what they are most likely going to do.
Sure, but all of those things could have been done by extending the existing protocol.
Also, fwiw, it has had media sends, presence and support for encryption for a very long time. The rest could be added. All of those things could have very well been an IRC client with a couple of extra features and a server upgrade to queue messages.