You're referring to decentralization of trust, while peer to peer means decentralization of compute and storage. You can have a system that is decentralized in

You're referring to decentralization of trust, while peer to peer means decentralization of compute and storage. You can have a system that is decentralized in one way but not another. A peer to peer system where every object must be signed by a centralized authority has decentralized compute/storage and centralized trust. The Apple ecosystem is probably the best example of that. Apple has to sign or notarize most things but these things are then sprayed across a huge diaspora of machines. A physically and computationally centralized repository of objects that anyone can create is the opposite. GitHub is a good example of that. The BitTorrent magnet network and most cryptocurrencies are examples of systems that are decentralized in both respects. Eliminating all forms of centralization without making huge sacrifices in areas like security or efficiency is really hard. I would say it's an unsolved problem since even if you try really hard centralization tends to creep in... e.g. how proof of work economies of scale create centralized mining cartels in cryptocurrencies. PoW is also very expensive, making it inefficient but moving that inefficiency "out of band" and hiding it in an externality. Decentralization is a big rabbit hole.