The reverse is true. There are other relays that are still functional as you'd expect in a decentralized network: https://zeppelin.social/
I'm coming from understanding nostr - each app usually starts with ~10 relays and as you start interacting with other people it collects more paths/routes/relays (the new "outbox model"). So as soon as you install any nostr app, it's usually not affected by any single relay issue.
IMO it's got all the bad things about centralisation and the bad things about decentralisation. The worst of both worlds. I don't bother with it.
Mastodon/fediverse and nostr (the latter despite being from the same founder) are much better.