No it wasnt the best design, and I think they went with OStatus in the end then activitypub. It never really was a facebook competitor. There was a while when Jan Broschardt was doing their UI that it was doing well, but the concept didnt work that great. Jan went to nextcloud which did take off. Now diaspora is 10 year old technology that it's going to be hard to upgrade. Some good things in there like a REST API. Things nostr can learn from, but it's not better than nostr, and wont become so. Should be able to all federate together with mostr.