Atom is pull, Atproto is push.

Atom was designed for news, before social media existed, where 15+ minute polling times were (borderline) acceptable. Atproto was designed for social media, in an age of Twitter users getting their news in seconds, to the point of being able to comment on live events play-by-play. There's no coming back from that world.

With that said, I wish both Mastodon and Atproto supported opt-in pull-based, static sources.