Social media is NOT sharing user created content. They are pushing for "engaging content", they have editorial styles, etc.
And it makes sense, nobody wants nor can read all posts if they were not curated.
But that means that social media companies are just content companies like news papers or TV. And they are responsible of what they publish.
Even more important, social media companies should be responsible for the Ads that they show. Scams are too prevalent in social media. Big social media sites profits from the ads, and the users are the ones that pay for it.