That wasn't the premise of the movie.
They repeat many times that the problem is a misalignment of incentives. Those companies needed strategies for monetization to answer to their shareholders and pay their employees in a modern market economy.
Unfortunately, those strategies had negative side-effects on the lives of users. That is what the documentary highlights.
Many of the interviewed people also mention the benefits of social media. They remind us of Steve Jobs' quote about technology being a bicycle for the mind. They are not calling for the extinction of social media. They just want to transform it from a drug back to a tool.