If other relays would not write your notes, then run your own relay.

The decentralization here is that everyone can run a relay and be part part of the global network.

You have been banned from one relay but you are still participating in the network. Imagine if you would be blocked on Twitter, would it be possible? No.

On Mastodon you would be able to register on another instance, but with completely new user, losing all your notes and followers.