It doesn't matter if lower layers are decentralized if the top layers are centralized.

Decentralization is expensive; it massively increases the coordination cost of adding coherent improvements to the system.

Even if the underlying components are decentralized, if the top layer (the way that all users access the system) is heavily centralized, then the system as a whole is effectively centralized.

Aggregators aggregate the consumer experience, creating a very small number of extremely empowered linchpins in ecosystems, no matter what the lower layers do.

Don't bother decentralizing the layers that don't matter to your problem.

Crypto decentralized the "database".

But what we need to decentralize is the notion of the app itself.