Lots of people, when their favorite work is subjected to valid criticism, will hotly respond that because the purpose of fiction is entertainment, "it's just a matter of taste" and "if you don't like it, don't watch it". I've already explained why this position doesn't hold water on the index page. But you might wonder, if story quality really is objective, and I don't dispute that the purpose is for enjoyment, why people have such vastly disparate opinions on how good the same story is. I'm making this article to point out all the ways this can happen.
One common difference is some people being okay with what I would call "unfair" storytelling, such as a plot that fails to foreshadow its twist, or the POV character lying to the audience. I think being okay with this stems from a lack of the virtue of self-respect. (The same thing applies to unfair difficulty in games, and I think that's what's up with Dark Souls's popularity.)
A similar thing is the valuation of agency. Some people care much less about seeing their favorite characters given agency than others, and this stems from a lack of appreciation for the moral value of Agency in real life.
Character glorification. How the audience reacts to a character being glorified or deglorified depends on how much they feel the character deserves it, and that of course depends more on the audience's values than any quality of the story itself.
Morals in general. These are a huge part of audience opinion. But of course not only are most people's morals pretty horribly messed up, but some people also claim that morals of a story aren't even a real thing. They say things like "it doesn't matter what the author thinks" and "it's just a story, it can't have an opinion". Of course, by telling yourself this you can severely reduce or eliminate the effect the moral has on your enjoyment. That doesn't mean it isn't there or that it isn't wrong.
Theme appeal. Themes of a story are another important part and this one genuinely is subjective. The themes a person wants to see explored depend mostly on the experiences they've had.
Brute-forcing. Most good stories have the hero in a pretty bleak situation near the end, and having them pull a victory out of it believably is hard. There are times when the writer does it by making the villain stupid. I think we all agree that that's lame. But another common cop-out is "the hero just tried so hard that he won anyway", which, while clearly unrealistic in most cases, would obviously appeal more to certain audiences than others. In particular readers strong in traits such as ambition and courage are likely to enjoy this more than readers who are stronger in prudence and rationality.
Preconceived beliefs. If people have preexisting conscious beliefs about how stories should be, they'll artificially feel that stories that conforms to their ideals are better. This is actually very similar to the flawed way most people go about deriving a moral system. Yes, I have preconceived beliefs about fiction too, but I can't count the number of times I've changed them because they didn't align with stories I felt were good. I change my beliefs about art when they don't align with my feelings, because I understand that the point of beliefs about art is to explain and predict feelings about art, not to replace feelings. But someone who doesn't see philosophy that way might think objectively bad stories are good.
I'm sure there are more possible reasons that I haven't pinned down, but this should shed some light on why my beliefs aren't contradicted by observed events.