Bluesky has been asymptotically approaching full decentralisation. A few years ago the gap was everything except a decentralised design, then it was AppViews, now it's "tooling and documentation" for the bit of the PKI that only 50 entities have done.
Meanwhile I lost my Mastodon account history because I moved once, couldn't interact with half the network or apps because I was on a non-Mastodon codebase instance, lost my account again because I stopped paying for access to the instance I was on, all classic signs of centralisation.
On Mastodon, if something goes wrong, nobody can cut you off the network entirely. On Bluesky, the author deleted an empty test account and is now blacklisted network-wide until Bluesky support decides to help. That is a classic sign of centralization.