@doriane You already got some pretty insightful replies here, I would maybe just add, and feel free to call me cynical, but all (most of?) the problems ATProto solves can be solved within the fediverse.
Eg. account portability with https://swicg.github.io/activitypub-data-portability/lola, discoverability with https://www.fediscovery.org, etc.
To me, what ATProto *really* solves is: coopting a grassroots movement with crypto VC funding and vibecoding. That's it.