Your supposition is flawed. I teach adults and there are three distinct components to that. I teach technology and design, but have applied the same principles to music instruction in the past, and many colleagues express the same concepts.
Factual — Part of any subject will be factual, foundational, and not open to debate. Music is codified upon a staff using notes. A student simply cannot draw butterflies upon a pudding and expect someone else to read it as music. The foundations of any discipline are what define that discipline.
Interpretive — This is where the individual explores, experiments, and bends the rules. What if I do this? If I combine these two things what happens? Tell a student that they can never use a G# in a particular song and guess what they will do?
Collaborative — The intermixing of ideas and experiences. Working with someone else changes your perceptions. Through challenging the other’s ideas, defending your own, and finding a way forward you end up somewhere unique.
Do music schools teach things that are not to be challenged lightly? Yes. But they also encourage moving beyond those foundations and putting your own vibe onto things. Knowledge and creativity are not opposites, they inform and empower each other.