> because you don’t want to teach each app to crawl PDS’s and subscribe to them
Why not?
If I want true decentralization, that means no central component. For the same reason that communities and individuals host their own RSS readers, each community will in the end also have to host their own relay and app view.
The benefits of decentralisation, including fault-resistance and censorship-resistance, can only manifest once every community is self-hosting their own relay and app view.