The idea of fragmentation depends on a model of decentralization that still makes the platform inseparable from the data it works with. AT separates concerns so that the priorities of your data host and the priorities of your platform host can conflict without one being able to control the other even if you don't self-host. All the reviews are just an entry in your PDS, so it's all there for any new or existing platform.
Thousands of people have already set up their own PDSes and it's inevitable managed hosts will appear soon. Blacksky just started migrating people over to its own PDS. AT's credible exit is close to reality after about two years while all the promise of ActivityPub and predecessor protocols has yet to materialize after over 15 years.
Thousands of people have already set up their own PDSes and it's inevitable managed hosts will appear soon. Blacksky just started migrating people over to its own PDS. AT's credible exit is close to reality after about two years while all the promise of ActivityPub and predecessor protocols has yet to materialize after over 15 years.