Been saying that for a while.
The problem isn’t just that people have to pay — but that proof of payment means nothing.
Choosing to display only messages to paid relays means giving these relays all the power to choose what you see.
Adding PoW wouldn’t magically solve it either (though would make it much better).
Unless you used a proper commitment structure to detect missing PoW, it would still allow for censorship— but at least you would only have trust that all the relays you’re connected to aren’t censoring.
With “just paid relays” you also have to trust the relays not to spam you.