The older I get the less useful I think this distinction between "official" and "unofficial" is. "Officially" King Charles can dissolve the UK parliament, but "unofficially" he can't. Power is power and we know it when we see it.
So yes I would call being banned or having your language limited by major global platforms "censorship", despite the fact that officially they're just private organisations.
You're just saying you only care about some people's rights and not others. Part of the 1a and the general concept of freedom is that you don't have to put up with people saying stupid shit everywhere, such as in your own home.
How? What about a bar? A stadium? Is it just the number of people to you, then? If I can pack enough people who agree with me into a field, do I now own that field?
You either agree that people who own things get to decide how those things are used, or you think that people don't get to own things. There's no "well, a lot of people use this thing" exception to property ownership.
Or, I guess you could try to nationalize the space since so many people use it, but I'm guessing "as you get older" any form of government is objectionable, despite this being exactly what you seem to want.
So yes I would call being banned or having your language limited by major global platforms "censorship", despite the fact that officially they're just private organisations.