In addition to the points raised by BMJ and in the comments below, there is a limit to what independent fact checking can accomplish. For example, are their fact checkers conducting their own scientific experiments validating claims and outcomes of a scientific paper? Are fact checkers reaching out to sources from a news article and verifying quoted information? When “breaking news” or “scoops” are reported presenting totally new information about the world, how can that be verified against other information that - by virtue of something being new - cannot be verified by other preexisting sources?
If the fact checking process is limited to verification based on other information that is currently available, and if the fact checking process cannot distinguish between factual information and the opinions people hold as a result of that information, the outcome will be an inevitable echo chamber that reinforces currently dominant views or whatever preexisting biases are present.
In short, fact checking is hard and there is a reason why reputable publishing outlets have their own internal fact verification processes before something gets published (including safeguards and retractions, because they make mistakes too), and why news is separated out from opinion-editorial pages... even if it is in style to add opinions (read: “perspective”) to every article.