I do really like ActivityPub as a general concept, but having it work by sending full copies of activity data for other servers to cache really makes it seem like it was written by incredibly idealistic engineers.

Like I could see the social and technological flaws in that from the get-go even if it took some nudging to realize the legal flaws.

(and I can also see the technological considerations that led to making that decision, though I don't think they outweigh the flaws that result from it, personally)