I believe social media is not inherently harmful or good per se. I'm not talking about the content, but the characteristics of the media itself. The internet has become roughly analogous to the Gutenberg Press, which had a spectacular influence on democracy, capitalism, religion, and just about everything else. Some of the internet's biggest publishers are found in social media.
Staring at a computer screen, or a smartphone, or a book rather than interacting with a group of people has the effect of severing us from a reality based culture. Social media has created new social circles not bound by geography. As the mind becomes 'synchronized' with an online social network, our comments may become more emotionally driven than rational, and critical thinking might occur less and less frequently.
Many social media site's AI algorithms interact, or 'synchronize' with us, turning the art of persuasion into a science. The illusion of free will is just one of their tools used to manipulate us, individually and collectively. They have created a cybersocial construction of what passes for knowledge and even reality, and we can’t get it out of our heads. Their AI knows us better than we do ourselves.
Avoid the harmful social media sites. Go somewhere that's worth it.