Personal data storage can be decentralized, although that’s missing the social part of the social network.
Identities are set up through a centralized system that in theory they could change, but I wouldn’t bet on it.
Relays supposedly can be decentralized, but need to handle all data on the network. So they require massive hosting costs that keep going up as more people use bluesky. Only large corporations can likely afford to run them, and that hasn’t happened yet.
There’s also reTux which is another game using the same assets.