Even sites that had a very good reputation like the BBC have increasingly been dumbing down their content and posting more clickbait in the last few years, and there are plenty of popular news sites (Fox, Daily Mail, etc) that are full of misinformation and trash.

There are several news sites that I used to regularly read (both global and local news) which I've given up on, because the combination of lower quality content, clickbait and terrible UX means that they no longer feel like they're worth reading.

So perhaps they need to consider whether some of this decrease in sharing on social media is down to the decrease in quality of the news sites themselves.