This really seems like a redefining of what the word Quality means to make some other point. "Quality is subjective" is a pretty poor statement since quality has a pretty objective definition.
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the standard of something as measured against other things of a similar kind; the degree of excellence of something: an improvement in product quality | the hospital ranks in the top tier in quality of care.
general excellence of standard or level: a masterpiece for connoisseurs of quality | [ as modifier ] : a wide choice of quality beers.
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Seems pretty simple applied to software. Intuitively does what it says it does in a bug free manner.
If you want to get into a discussion that parallels why people call modern art great and there can be no standards for what is art, then I'm really not interested. I don't believe a white canvas is art, and I believe software and art can have objective standards.
For example, consider a team that wanted to hire people that they considered 'Empathetic'. Firstly they would need to define what they consider good signals of this, secondly they would need to share some kind of system of measure of it, and then finally they'd be able to optimise for it by trying to create the context and behaviour that they believe would increase its likelihood (e.g. hiring people that went to a lot of Empathy training days at their previous companies).
My point is that the definition of quality is objective but abstract. In practice it refers to a concrete property that you wish to optimise for, and this choice of how and what to measure as quality is a subjective decision requiring coordination.
That does not mean it's not a useful concept, and that therefore everything should be considered equal. Most people prefer to act with regard to their preferences, and that is why people often talk about something called quality even though it's difficult to pin-down.
(This is conceptually similar to Merit which is another abstract word people use to help coordinate human activity.)
Thats an important distinction though. While it is difficult pin down whether something individual is quality or has quality, it is easy enough to compare it to something else and say whether it has more or less.
When most people say "this is a quality _______", the comparison is implicit.
I agree with you that a common property of a 'quality' is that it can be compared (without this property it would not be measurable.)
When people say "this is a quality _______", I think it's useful to ask them why that is Good, and what properties it had that helped them realise it was 'quality'.
Plain disagreement about the usefulness of the concept of measuring and optimising for certain properties annoys me, because often the people that do this are just trying to replace the original system with one of their own.