That's just not true though when you consider that these platforms have algorithms that will determine which posts get more visibility than others (trending is the most obvious of these). I don't think this would be even half as much of a debate if we had an electronic platform that could actually be the modern public square of the US, but instead we have only private entities attempting to provide this, and they are decidedly not protectors of free speech (that would be our government). The extension of this is that even if the government did provide such a platform, there would likely still need to be rules because as much as you like to think we have unfettered free speech, you still can't stand in the middle of the public square and call for the death of another individual or you can't shout "FIRE" in a movie theater when there is none.

If we actually had a government run system, we could ensure things like accountability for your ideas that you self publish in such a public square because the government itself would have the servers that contain the data. The constitution would limit the government from censoring this platform, but it wouldn't limit the government from implementing more effective methods of processing abuses of free speech such as libel by having an immediate record of what was said. My main point here is that it's easier to agree on what if any free speech limitations should apply if there isn't this proxy layer of "Well corporations can do whatever they want with their servers" and "Well these laws don't apply to what they said because nobody is speaking in the domain that freedom of speech applies to"