The current generation not knowing how to communicate without social media does not imply or suggest that social media is necessary for communication. If a person believes their values and entitlements limited by private entities they find alternatives not facilitated by those private entities, as in alternatives to social media.
I too agree that social media as a common medium probably does not, in itself, confer "common carrier" status on it. Even if many have been bought up by Facebook, there is still room for competitors to arise that provide alternative. This is not like ATT&T before its breakup where it was literally the only option. Heck, nothing stops someone from rolling their own stack on a local PC or local "cloud" and running their own social media service there, with mobile friendly sites that don't need an Android or Apple apps no need to rely on 3rd party cloud infrastructure. Then they would only be relying on the common-carrier ISP infrastructure that couldn't ban them for content. They aren't entitled to use the private infrastructure services or content distribution networks of other private organizations.
Generally speaking, hate speech can be allowed free speech, but not advocacy or incitement of specific violent acts. As the platform owner, and absent additional guidance from courts or Congress, private companies have no choice but to make decisions about what can be done with their private property. No company that is not a "common carrier" is obligated to let their infrastructure be used for a specific purpose. If you don't like the choices they make, the root cause isn't with the companies, it's with the laws themselves.
There is a sort of slider here between speech & property. If you dislike companies controlling their platforms as they see fit & want the slider to move in favor of free speech, it moves against freedoms of private property.