Sure, it is in Facebook's best interest to keep you on the site for as long as possible so that they can drive ads. But the same issues with social media existed before Facebook had ads. People would still be checking their feed constantly, checking if their post had new likes, seeking the approval of their peers.
One of the interviewees said he was addicted to his email... what bad practices does Gmail employ and how exactly are advertisers to blame for this as well? Gmail has a couple of ads but that's about it? It also said Whatsapp was one of the apps responsible for the spread of fake news, this is simply a texting client with the ability to send messages to groups.
Maybe it turns out that if you put technology and instant messaging in the hands of social circles, messages, whether fake news or not, spreads faster than ever.
If Facebook had no financial incentive, sure, maybe they would have realised the negative effect it is having on people and shut the whole thing down. But then another site would have come along doing exactly the same thing. Maybe the issue is that people don't cope well when being connected with hundreds of "friends", constantly seeing updates from their lives and feeling compelled to also share updates of their own.