More importantly, this stuff also isn’t completely subjective - even though there’s absolutely room for preference. The limitation on subjectivity is the fact that we all generally have ears. Even though there may be some variation on how people want their music to sound (or potentially even how things are heard), there are certain facts about human hearing that need to be taken into consideration. Moreover, we also know the kind of balance that most people prefer, along with what the other groups prefer. So while that doesn’t say anything about how individual people are going to enjoy things, we can at least reliably predict how it’s going to be received by most people, and this gives a strong foundation for being able to evaluate headphones as well.