If somebody speaks in the woods, and there's nobody there to hear it, do they make a sound?
Yes, they technically have free speech, but in reality not really.
The purpose of speech is that you might persuade somebody else. If there's nobody to talk to, you might as well not speak at all.
You can speak all you want in public spaces, on your own property (whether that be your home, your blog or your mastodon instance) mostly without limit.
But Facebook, Twitter, Google, HN or any other private organization is under no obligation to host or amplify your speech.
The government can't censor you and you may speak your mind in public spaces. You may also do so in private spaces, with the permission of the owners of those spaces.
You seem to be under the misapprehension that certain private actors are required to allow your speech. That's not true. They are responsible only to their shareholders and to a lesser extent, their customers -- and in this case their customers are advertisers and not you. You are the product being sold.
If you don't think that's right or fair, then don't interact with those private actors. If enough people chose not to deal with them, they would lose their power and influence.
I voted with my feet years ago. If you haven't, then you're part of the problem and not the solution.
When capitalism revealed its ability to create abusive monopolies, we created new laws to mitigate those harms.
When the whole worlds discourse flows through a few centralized social media companies, as a society we are free to imagine new legal concepts and regulations to deal with the unforeseeable consequences of these new phenomena.
Where did I say that wasn't appropriate?
I strongly believe that those big social media companies not only have too much power and influence, but that their business models are exploitative and morally repugnant.
Which is why I don't use them. At all.
In fact, I detailed[0] how I thought this issue should be dealt with the other day.
I can't find it at the moment but there was recently a court case where a judge ruled that the constitutional right to Assembly was not infringed by pandemic restrictions (It is illegal in several US jurisdictions to assemble with more than N people in a private space) because people could freely assemble on online platforms like Facebook and Twitter. If the digital public square does not allow for free assembly, and the government forbids you from assembling in a physical public space, then it seems plausible to me that we have constructively eliminated certain constitutional rights.
0: https://en.wikipedia.org/wiki/Freedom_of_speech_in_the_Unite...
If you can't convince enough people that your message is worth propagating, maybe it isn't. If you can, you will have the means.