Not everything fits in a spreadsheet
It always boils down to providing useful and insightful information (with a dab of style and humour) on a consistent basis, says the middle age vet of small town print and digital media products.
"...Experienced editors know good work"... Not sure it's enough, even though I agree with the overall message. In my view, there is often a vast distance between what editors commission and what their publication's mission statement is. That's a problem. Commissioning good journalism could be misplaced or not aligned with product market fit, if an audience expects something equally good, but different from a publisher. You and I have discussed it - content strategy needs to stick to satisfying specific user needs. Without it we'll continue having lots of generic brands and lots of display ads models (which superficiality is being found out by the advertisers anyway).
I'm in content marketing & SEO for B2B software and one of the key things is to remember that not every post has the same job. You shouldn't expect the same results from each.
Totally agree that there cannot be a one-size-fits-all metric. Instead, evaluate it on the *type* of posts and write different *types* of articles i.e. a listicle will perform differently than an investigation.