The problem is algorithmically driven content feeds and the lack of transparency around them. These algorithms drive engagement which prioritizes content that makes people angry, not content that make people happy. These feeds are full of misinformation, conspiratorial thinking, rage bait, and other negativity with very little user control to protect themselves, curate the feed or to have neutral access to news and politics.
Lemmy sorts content very simply based on user upvotes. If you want to know why you're seeing a post you can see exactly who upvoted it and what instances that traffic came from. It's not immune to being manipulated but it can't be done secretly or in a centralized way.
Yet based on their actions we already know that Facebook has levers they can pull to directly affect the amount of news people see about a specific topic, let alone the source of information on that topic. These big social media companies guard these proprietary algorithms that are directly determining what news people see on a massive scale. Sure they claim to be a neutral arbiter of content that just gives people what they want but why would anyone believe them?
Lemmy is not the same thing, though it's not without its own problems.