I read that portion not as arguing that every possible metric is completely subjective, such that some people will actively prefer, for example, a version that doesn't last as long, or costs more for no additional benefit, but rather that quality has a lot of different axes, some of which are mutually exclusive or in active tension, and the relative weighting of different axes is purely subjective. There is no way that one can argue that it is "correct" to value durability over cost. Or aesthetic appeal over simplicity.

Basically, when there are many axes of quality, the pareto frontier gets very large and very complex and no one position on it is inherently better than another, even if everyone universally agrees which direction is "better" on every individual axis.