Yep, all this ^^^

This is also one of the reasons why I believe ActivityPub client-to-server failed and will likely never gain much traction. It either needs every single client to re-implement all the features it wants from scratch, or the entire ecosystem needs to be dumbed down to fit a single mold. Leave all the unique functionality in “uncommon” software like (streams) and friends, even software like Lemmy or PeerTube would likely be extremely difficult to build in a world where client-to-server actually became a thing.

The only way I can see C2S actually taking off is as IPC between an “app server” (which would be the equivalent of Mastodon or Lemmy or (streams)) and a “federation server” which is just a dumb pipe that distributes and receives objects and activities, and even that has it’s fair share of concerns, both around efficiency and the same “dumbing down” problem.