I certainly am not advocating that social media companies should have even more control over our lives. I would like them to have less, which presumably happens either because (a) we stop using social media (at least in the current sense) and/or (b) more options for "social media" platforms emerge.
Since (a) is unlikely in the near term, that probably means (b). I don't how Twitter banning anyone (including POTUS) from their platform does anything but encourage that.
I also don't see how "large corporations that have used psychological manipulation and network effects to become really popular must be consider public utilities, despite no law to that effect" really lines up with free speech. Do you believe that the NY Times should be required to print my op-ed's in their online version? How about my comments on their articles?