1)  People can and should post to multiple relays. I've seen people post to 17 or 25 relays (I recommend against that, but there is nothing pushing them to not do it).  So if I relay bans them, they don't fucking care, they aren't going to have their post removed from a dozen relays. So in essence, this is very good censorship resistance.

2) Unlike Mastodon, if you get censored from one relay, you have already moved somewhere else because you are posting on multiple relays.  You just drop that one and perhaps replace it with a new one.  In the mastodon case, you lose your account and all your followers.  In the nostr case you only lose an unimportant relationship with a relay you no longer like, and your followers don't even notice.

3) If clients are just using a few big centralized servers, then those client authors misunderstand the whole point of nostr.  Choose a better client.

4) If "nobody is listening" to the relay that you advertise as the one you now post at (when you move), then that is only because their clients are not doing nostr in a decentralized way (the outbox model).  You are right to notice something is wrong with their model, but it is not something wrong with nostr itself.

There is a tension between being being distributed + censorship resistant, and maintaining client privacy.  Some people want to provide better client privacy by not connecting to "strange relays" at the expense of censorship resistance.  That choice isn't right or wrong, but it isn't the choice I would make.  My stance is that privacy should be done right - via a VPN or Tor - and that nostr decentralization and censorship resistance can be maximized without sacrficing privacy when privacy is done right.

And finally, yes relays will censor. If you put illegal content on my relay, why should I risk my neck for the illegal content of someone I don't even know?  It is your job to find a relay that allows it. This feeling of entitlement, that relay operators must host your content, that you are entitled to their hosting, should really be re-examined.  We need to maintain liberty and freedom including the liberty of relay operators to host what they choose (and only what they choose), and yet still we can provide very sigificant censorship resistance by breaking the connection between central providers (twitter, mastodon servers) and your personally managed identity.

I hope you understand that this is the best we can do.