IP is super decentralised. Digital communications could have led to a more decentralised society than ever before, and in the beginning , they end. But in the end, they didn't, because large actors figured out how to exploit them.
1. Assignment of addresses is centralized. Even though it's federated (ie distributed), authority still flows logically from one single authoritative view. And even though individual networks can choose to go against that central view, diverging too much prevents them from talking to one another (ie most of the bargaining is on a take-it-or-leave-it basis, rather than something more nimble or adaptive)
2. It's a protocol for communication between nodes. Reusing node addresses as service/contents addresses leads to services being inherently centralized on those (logical) nodes. Not a problem with IP itself, but definitely an attractive nuisance that made problems for things naively layered on top of IP like HTTP(S) and DNS.