I think the responsibility for combating fake news lies partly with individuals — we all need to learn to check facts before sharing something, no matter how much we agree with it — but it also lies partly with online services.
Many online services these days are designed around maximizing user engagement. They encourage users to share things, like things, and comment on things, because the more that happens, the better the engagement numbers look, and the better the company looks to investors.
But some of the most engaging content is content that makes people angry or indignant, since that makes them more likely to reply or share quickly without thinking. This ends up incentivizing the rapid spread of emotionally charged misinformation, and it de-incentivizes calm, thoughtful reflection. Some social networks thrive on this, because more eyeballs and more clicks means more ad dollars.
Online services need to shift their incentives toward rewarding thoughtful, beneficial content and away from emotionally driven, rage-fueled content or the fight against fake news will continue to be an uphill battle.