Yes that's my understanding if a relay nukes your content its gone, but you can post to multiple relays and "trust" that one of them would hold it because nuking peoples content wouldn't be good for people using your relay
Or if you want complete control just run your own relay
Full decentralisation does rely on each user being able to run their own node/server/relay, so it's a noble goal. However, without a consensus of the kind that is achieved on Hive, for example, many needed features are missing.
From what I can see, most of the items in the list of failings of Mastadon on the Nostr Github page also apply to Nostr.
Can you provide an example of features that are missing that would require consensus?