Twitter I can delete. I don't browse facebook, I try not to browse instagram - but these platform's messaging facilities, along with whatsapp, google chat, signal, telegram and more are used daily by my friends and family to communicate.
Sure you can simply cut off those who don't use your preferred platform. But I've seen what happens to people who do that - when the first facebook backlash occurred back in the late 2000s. They disappear from the real world 'social graph' of their non-local friends.
Of course it would be better if everyone used one, encrypted messaging app. But thats not likely to happen any time soon. Of course social media is a poison, as OP pointed out. But its utility for low effort passive relationship maintenance with my old friends from college, jobs, school etc is an essential part of my social life. I suspect thats true for millions of people.