Sure, you can control you data (nobody can author notes on your behalf, or ban you from signing new notes).

But if everyone is centralizing into a very small number of relays (if you want to be where everyone is you'll have to), then these relays will, just like big tech, have too much influence, and yes, they could silence you here on Nostr.

But wait, I can just use a different relay then because that's the power of Nostr, right?

Yes, except almost everyone is using the centralized relays so you'll be in a secluded network with barely anyone over there.

Nostr needs to do a better job at being a singular (not a fragmented) Twitter clone.