We know. But you also know, if there are monopolies, even if they are private, they can meaningfully limit the flow of ideas in a way that is highly problematic.

And the term censorship is broad, and isn't specific to private entities versus government. Just because we don't have a Soviet-style government (good), doesn't mean that automatically everything is free and open. If I buy out all of a particular work of art and burn it in a bonfire, I've committed censorship. If not illegal, it should at least elicit some moral eyebrow-raising, no?