Boredom can produce great thinking. Social media mostly wastes time and clutters the mind with crap - crapola like what the Kardashians are eating for lunch today, useless videos of dogs and cats, and the latest crap superhero franchise movies.
Yes, you're right. Of the sites you reference, the only one I use is Twitter. Those animal videos are fun. And when there's some kind of crisis, you can find a lot of information, reliable and unreliable. There's also good political discussion. I enjoy seeing what mad Italians have to say about bad food, and reading the views of Lake Superior.
But you can spend a lot of time there, not intending to do so. You could also be reading a book. Or making a fox laugh.