Just a quick overview of different social media platforms, the word decentralized, and what it means.
In my opinion, decentralization requires 2 parts: the spread of data over multiple sources AND your complete control of where that data is distributed.
That being said, Fediverse IS decentralized because there's 20,000+ instances that can host the data AND can control where that data goes, if they want. This still means that you have to run an instance to have complete control, but running an instance is cheap and easy enough.
Nostr is also decentralized with your data going to hundreds of relays, but the control just isn't there. On Nostr, instead of instances exclusively hosting the data, there's relays that each user has to connect to. You can choose which "relays" have that at first. However, if anyone from your relay is also connected to another relay and boosts your posts, it will get relayed. Also, there's no surefire way to edit or delete content on Nostr. Some apps let you "request" a deletion, but it's not certain that it will be honored.
Threads is NOT decentralized because even though they allow sharing TO the Fediverse, there's currently no way to control which instances will see that data. There is blocking for individual users, but with a decentralized platform like Fedi, that's not enough.
BlueSky, on the other hand, is NOT decentralized by default. You CAN have control of your data if you host a PDS, but that data can only be used on BlueSky right now. There is the 3rd party "BridgyFed" that users can use to federate their posts to Fediverse, but beyond blocking individual users, BridgyFed is in control of which instances will get that data.
All-in-all, Fediverse is currently the only social media platform which allows nearly full control over your data and where it goes. This platform is the future. I just hope everyone else sees it that way soon enough.
