If you can build your own or selfhost each of the following to read and push back to all of the atProto protocol:
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App
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Backend Relay
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Moderation
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Algorithm
And you still say that's not decentralized I'm not sure what you're looking for nor what your definition of decentralization is.
Used Mastodon for two days. Not a great platform imo. Been using Bluesky for a few months and having a decent time, but sometimes it's hard getting fed the content I want (not sure if it exists in general there).
Also have been a decently heavy Twitter user since 2013 ish