I think a lot of people think big social media platforms are actually communication platforms, they're not. They're designed intentionally to be difficult to communicate on.
That the not the purpose of them, it's in the name 'social media' they are the media, you are the social. They are creating media based on the things users post. They're not made to facilitate communication between friends, family, coworkers, etc...
They are designed specifically for users to generate monetizable content and data. They use a veneer of 'connecting the world together' so users will generate content that drives clicks and makes them money.
A true global communication platform would look nothing like the social media we have today. It would be designed around allowing people to communicate easily and freely, it would give you control over who and what you interact with and it would allow you to maintain granular levels of privacy.
Ya know...like other systems designed to facilitate communications...like say the telephone system...