Social media leveraging the billions spent on marketing over the years, the skills of knowledgeable experts in multiple disciplines, basically thousands of human years of experts at manipulating people against a random person with zero guard up that wants to chat with their friends/make new friends isn't a people problem.
Designing social media as a positive place was and continues to be a choice that no one is making. Because it's too damn profitable to make a hellhole / attention vacuum that people can't stop using.