Many odd things about this chart, but mainly it serves an inadvertent reminder that “bias” is a terrible proxy for quality or reliability. Mother Jones is absolutely in the correct column, but they do better and more accurate reporting than many of the less “biased” outlets. 
Also unfairly bundles together on each side opinion journals that are generally good about factual accuracy with clickbait farms that absolutely could not care less as long as they get them clicks.
In principle you could have a wildly unreliable perfectly centrist outlet that was ecumenically unscrupulous about running Federalist trash and Alternet trash. The reason you don’t see it much has less to do with editorial bias than the economics of audience bias.
There IS a correlation, but it’s in a sense epiphenomenal. Catering to a specific ideological audience gives you the *option* to be garbage, because you’re selling validation of priors, not useful information.
The obvious asymmetry is that the left column has outlets that are both factually reliable and do significant original reporting. In the right column, you have opinion journals with standards, and sites that purport to do reporting that are trash fires of varying intensity.
Not coincidentally, the left outlets doing original reporting tend to be hoary old pubs with strong institutional cultures. The ones on the right are newborns, and the quality of reporting enormously more dependent on the individual writer.
The garbage clickbaity outlets on the left also tend to be of relatively recent vintage. The difference is they’re eclipsed by older ones with standards that don’t really have equivalents on the right, for a variety of historical and sociological reasons.
Also even the spry young online mammals on the left side are likely to inherit a little rigor because they can staff editorial by poaching from the dinos.
Maybe ironically, the left outlets are much better on average because they have (in one sense) a much more conservative professional culture—bodies of inherited norms and traditions. (I can’t say I’m very confident that will remain the case in 20 years, alas.)
