Quality comes from the inside. The inside of your mind. From your unique thoughts and experiences that can't be copied by anyone else. That's why great art is unique, and vice versa. Because it's the same thing. That's why you can't measure quality, because it can't be compared to other things. That's why you can't copy real quality or repeat it on a schedule, because then it stops being unique.
That's also why real quality survives all trends, because it can't be replaced by anything new, because nothing else can be like it.