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.
The US Founders thought that people must have the ability to speak their mind, to discuss and challenge each others ideas. They thought this ability was so important they enshrined it in law.
public speech that expresses hate or encourages violence toward a person or group based on something such as race, religion, sex, or sexual orientation
Free speech doesn’t mean you’re protected to speak whatever you want in any setting. Speech is subject to private property and common sense. If you are profane on my property I’ll kick you out and ban you. That is NOT a violation of your free speech.
You mean a society where the most charismatic/popular members get the attention of the masses, mostly by telling them what they want to hear? Yes, I think I'm prepared to live in such a society.
I think, in your attempt at making free speech look undesirable with your mention of "amplification", you forgot that this amplification is for everyone, including you and those who agree with you.