Bluesky's political theory is basically Withering Away of the State
https://en.wikipedia.org/wiki/Withering_away_of_the_state - decentralized only in theory with a promise of maybe being in practice.
Mastodon is fiefdoms. The admins have freedom by running their own server, but in general users tend to be even less free than on big tech platforms, because at least on big tech platforms they have some expectations surrounding the rules, while on Mastodon users are at the whims of a potentially volatile or emotional person.
Nostr is the only place with traction where the users are actually in control. Your cryptographic key is your identity, and the fact you hold it directly means you can participate in the network freely at any level. Instead of top-down control, users self-govern into "web of trusts" and small communities that they opt into. It's arguably not ideal for a "public square" though, since spam is hard to control when you can see everyone. It's best for strong connections with people you already know, and people they know (mutuals), because you can filter the network into small groups. Therefore what excites me most about Nostr are the use cases that inspire people to go outside and connect with the people around them, their friends, and family, eg
https://birdstar.app/ and
https://treasures.to/ .