some relays do sync between them. there is a gossip model where you can find what relay a specific user has published to and then read from there.

Exactly - some relays sync between them, but even if you follow me, you might not see my messages if I'm not being synced, or don't post, on the relays you use. I still fail to really understand how this is decentralised. Mastodon's model is; but Nostr seems to be entirely based on a few relays.

"can" isn't the same as "do".

That's a very bad drawing that makes my point. It shows Nostr clients posting to separate relays, none of which talk to each other. In order to read a post, you have to connect to a relay that carries that post. But unlike ActivityPub's instance-based infrastructure, it isn't immediately obvious how to find out what relays this post is on, or where I post on Nostr. Every time I come here it's clear that Nostriches are wilfully ignoring how poor this system is, and how the entire power of the platform is hanging off a few big, censorable, relays.

I see what you mean. I used to think that too. What client are you using ? For me on Amethyst, seeing and adding what relays you are posting to is as easy as sidescrolling on your profile and clicking "Relays" . There is nothing preventing relays from speaking to eachother and it has already been pointed out that some do, through mirroring. As a simple open protocol, if a relay begins censoring or if a 100x scale up in users occurs, both relay diversity costs and spam prevention through zaps and and subscriber relays, has been part of the design from early on (and tor). From a user perspective or relay provider Nostr is just KISS. No email signup, host lock in, version compliance/updates. Just nsec/npub , json parse and go. If you don't see the elegance, i'm not quite sure how to describe the beauty any better. You like ActivityPub. Do activitypub ! It does not need to be either/or. For me AP is an overdesigned make-work program for specialist, like Lighting Network or Kungfu. Nostr is the Brazialian Jiu Jitsu of social protocols. If you like larping at decentralization, do activity pub! If you are trying to survive an uncooperative street fight, Do nostr. https://image.nostr.build/f073e407c4f792a491adc199a32a63ce86c508ed713a71329c7ac7ca91f2264f.jpg#m=image%2Fjpeg&dim=587x945&blurhash=%5E99ZNTOf%3FKV%3FISoQF%3A%3FJjCohS5Im%25OX0xwayNFWG%3DfR%23%252s%3AaeR-JN%24-W9X8bJV%3FNFW%3FS2smo3NaMwsYn%25S1s%3AsA9rsZNFjFt8j%3DIms%3FNFR*t8bY&x=bb7d897bec6171b0c5dce204d8e252000ca09f0feb3e8d4cb33e8856aa0aa407