We should clarify that "free speech" is unrelated to what Twitter and Facebook are doing. Free speech is a constitutional concept, protecting people from draconian government laws that suppress their speech, or discriminate them based on their speech.
What Facebook and Twitter are doing is providing a product that amplifies and places speech in front of particular eyeballs and ears. There are many, many issues with what Facebook and Twitter are doing, but they're all unrelated to the legally-protected constitutional free speech.
Some people have argued that "posting on Twitter/FB may as well be considered protected speech, since society depends on it so much" which is an interesting concept for sure, but has no basis in law yet.
Finally, to your last point, the amplification is not for everyone, and that's at the core of why people hate these companies right now. Users are subjectively amplified or suppressed, or kicked off. And this unequal treatment of users is at the very core of their business model: they make money by selectively amplifying content.