The fediverse correctly prioritized the ability to scale down and to have many co-equal participants in the system. I believe this is critically important. Directed delivery of messages is what makes this possible.
The ATmosphere correctly adopted content-addressed storage and decentralized identity, something I have been arguing that the fediverse needed since before ActivityPub finished standardization, but which by and large the fediverse developer ecosystem seemed uninterested in until recently. But nodes going down is a thing that is really stressful for many participants, including in choosing a node, or even daring to self host
It's possible to build a content-addressed system with directed delivery. I have been arguing towards that direction since 2017 https://github.com/WebOfTrustInfo/rwot5-boston/blob/master/final-documents/activitypub-decentralized-distributed.md