come to think about it, the framing of good/bad is rather useless when it comes to art, isn't it? liked/disliked seems like a more useful way to frame it.
i assume most of the time, people calling something "good" just use it as a shorthand for something they liked. in the same breath one could say "i like this, this is good" and it's just emphasis, but sometimes it isn't. "this is good" implies something. good in terms of what?
when i say "that's a good movie" or "that's a good song" or "that's a good drawing" i often mean, "i like that [thing], and i think it's very likely that you will like it too, based on what i guess you like, or just what i guess many people will like". it is often an assessment of the preferences of hundreds of thousands of people, based on mostly intuition and a dash of statistics. i don't like making such an assessment very often, because i don't like guessing other people's preferences.
it is also never a real assessment of "quality".
i honestly think there is no such thing as artistic "quality" or "value". what i see is usually measurements of effort plus attempts to quantify how impressive a given piece would be to a fake, unknown, "neutral" observer. but effort is just one aspect of the art process that, while it can affect my perception of a work of art, is probably best considered separate to that work, especially considering how difficult it is to accurately assess effort. and, there is no neutral observer.
quality does work as a concept in other things, things we use and deteriorate over time like a mouse, or a hammer, or a pen, or a refrigerator. art doesn't deteriorate over time, only the medium used to preserve it, if any.
i suppose it could be argued that quality is rather an assessment of the amount of mistakes in a given piece. not purposeful "mistakes", not stylistic decisions to counter perceived notions of what is aesthetically pleasing, but rather honest failures of execution. if i am in a marching band, and i play the wrong notes, or am off-tempo, i might stand out as having "made a mistake".
but that is a difference between intent and reality in a performance, and there is not an absolute, objective law that determines how many mistakes there can be in a performance before someone can not appreciate it anymore. it can be confusing, or comedic, or endearing, or a myriad of other things entirely by accident. there are cult followings for plenty of "bad movies".
is categorizing these works as "inferior" in any way useful? if it is about managing expectations, or being able to share the experience of enjoying these works with others, what is the difference between discussing them in terms of personal taste, instead of a purportedly objective "quality"?
"i like it, but you might not like it" works regardless. "i like it, but i shouldn't like it because it has a lot of mistakes" is a bizarre idea to me. i suspect it doesn't do anyone any favors and is entirely worthless. i really doubt perfectionism will ever cease, no matter how hard millions of people enjoy looking at "trash".