> In most fields (film, painting, music, etc), there are standards -- agreed upon to varying degrees, sometimes almost unanimously, sometimes with only a plurality -- based on objective or almost-objective criteria. In other words, there are "measurable" criteria that expert or even merely good practitioners can agree on. In these cases the word "quality" is often used as a shorthand for possessing these kinds of properties. In this sense, ascribing quality is functionally different from a mere opinion, linguistically and technically.
Could that be selection bias, where people who think X is "quality" promote other people who agree and push down those who disagree?
At that point, it may be true Agree X has found something objective and measurable, but they're using circular reasoning: these metrics are important because they show "quality", and we know it is "quality" because of those metrics.
It's true as I noted there is no final god-like arbiter. But that is not really an interesting observation imo. Taking that perspective to its logical conclusion we end up in a world where values are utterly flat and relativist, and the only thing we can say is that we can't say anything about anything.
It's also true the selection-bias you described exists, in some cases to the point of collective delusion. But note how I can say that and you can immediately think of cases that fit and cases that don't...
On balance there is something real and (despite my first sentence) I want to say "objective" in most cases of expertise. In practice everyone lives as if that were true, even if they are arguing otherwise.
Regardless, even if you want to make the most contrarian, relativist case possible, the phenomenon of expertise (simply viewed as a social pattern) does exist and governs nearly every domain where people talk about "quality".
Could that be selection bias, where people who think X is "quality" promote other people who agree and push down those who disagree?
At that point, it may be true Agree X has found something objective and measurable, but they're using circular reasoning: these metrics are important because they show "quality", and we know it is "quality" because of those metrics.