I'd like to highlight Adam Neely's video on the subject [1] (also pointed out by user guerilla), where he argues quite convincingly that 'music theory' is not the theory behind music but theory behind the particular subset of Western music.
That doesn't make it any less useful for creating this type of music, but it's in no way a universal theory, or arguably, a theory at all. More a collection of rules and conventions used in Western music.
I've got a degree in classical performance (and deeply love and respect that tradition), but more often collaborate musically with people who don't come from that background. Most will say with a little embarrassment that they wish they knew more "music theory". It's difficult to communicate to, say, and indie songwriter how I think theory might help them (to communicate, or analyze their own or others' music), and ways it's probably totally irrelevant (depending on genre, functional harmony is really not very useful).
And that's still just western music traditions. Study Indonesian music and you can see how many ideas about music are encoded even into the notation of western art music.
If there were aliens physiologically equal to us, I'd bet they'd come to a similar set of conventions and it (their copy of our western tradition) would be the most popular musical tradition in their planet: 12 intervals separated by the equivalent frequency distances, etc. They'd probably have different (saner) names for the notes, but it would be the same kind of music.
That doesn't make it any less useful for creating this type of music, but it's in no way a universal theory, or arguably, a theory at all. More a collection of rules and conventions used in Western music.
[1] https://www.youtube.com/watch?v=Kr3quGh7pJA