No, the main argument is that the main relay is, and for the foreseeable future will be operated by bluesky. This means that bluesky can decide what is and isn't visible, but that's not my biggest issue: to me the bigger problem is that bluesky sees everything that everyone says or thinks about anything.

Yes, it is possible to change. As TFA says:

But every counter-argument to the concerns above rests on the same foundation: technically, users can leave. Technically, you can self-host. Technically, you can run your own relay. The capability exists at every layer. But people don't do these things. They never have with any protocol. Not email, not RSS, not XMPP. The default wins. Always.

It doesn't matter that a few can be free: the vast majority goes where the lowest friction is because they have their life to live, and the lowest friction leads to the centralized bluesky