It's technically correct while also being practically useless.
There are no fundamental rules to grammar, but we still teach writers what a simile is. Even in spelling, English has no consistency about a lot of this stuff. Are spelling rules useful though for non-native learners? Heck yes. Do we still have grammar books? Yes. It turns out that learning the exceptions is sometimes faster than memorizing everything. Music is a communicative medium based in large part around social norms of what combinations of sounds tend to feel good to people who grew up in a specific environment, and music theory is an attempt to break apart that social consensus into basic rules that can be imitated and built up into more complicated genres.
The rules are somewhat arbitrary and made up, but that doesn't mean they're not real, and that doesn't mean you can't sort-of derive some of them from more basic rules or from basic principles.
Music could have gone in multiple directions, but for whatever reason Western music went in the direction it did, and many people who are trying to learn music aren't trying to learn the full spectrum of every direction music could have gone. They're trying to learn how to imitate Western sounds, and for that purpose specifically music has rules -- many of them derivable from other rules, flexible and breakable as they may occasionally be.
There are no fundamental rules to grammar, but we still teach writers what a simile is. Even in spelling, English has no consistency about a lot of this stuff. Are spelling rules useful though for non-native learners? Heck yes. Do we still have grammar books? Yes. It turns out that learning the exceptions is sometimes faster than memorizing everything. Music is a communicative medium based in large part around social norms of what combinations of sounds tend to feel good to people who grew up in a specific environment, and music theory is an attempt to break apart that social consensus into basic rules that can be imitated and built up into more complicated genres.
The rules are somewhat arbitrary and made up, but that doesn't mean they're not real, and that doesn't mean you can't sort-of derive some of them from more basic rules or from basic principles.
Music could have gone in multiple directions, but for whatever reason Western music went in the direction it did, and many people who are trying to learn music aren't trying to learn the full spectrum of every direction music could have gone. They're trying to learn how to imitate Western sounds, and for that purpose specifically music has rules -- many of them derivable from other rules, flexible and breakable as they may occasionally be.