For instance, CNN is left leaning and Fox is right leaning. They should just explicitly state their viewpoint so viewers can calibrate how much credence they give to unsourced claims and see past the political posturing.
I see it differently, subjective opinions aren't journalism.
It is a true statement, but it doesn’t mean that all models are equally wrong, or that all journalism is equally biased. Objective journalism is an ideal to strive for, even it if cannot be perfectly achieved.
While I agree that NPR puts out a lot content that can be described as 'lefty', NPR News feels pretty straight down the middle.
Personally, I find the https://realclearpolitics.com model of just putting headlines from different outlets in a list to be more useful than outsourcing some sort of "bias rating" and "fact-checking" to YAMO (Yet Another Media Outlet).
I think the real subtext of this chart isn't so much to portray any particular outlet further to the left or right than it is, but rather to boost the credibility of fringe outlets.
That being said, I do appreciate that allsides uses an interesting method to blind bias surveys to help categorize. But sometimes things don't always line up.