They still have theory. I have an amazing book on playing Rajas. But if I played them right now, it would sound more like messed up blues because I haven't learned that aspect of how to play Raja music correctly, and only by coincidence the blues pentatonic scale is similar. I have an idea what Raja sounds like, but that's rather incomplete knowledge of the associated music theory. Applying the wrong theory produces the wrong sound. Enough evidence that there is theory in all forms of music.
You might be right about a certain western bias toward [western] theory, but it has no bearing on theory in general. Especially how it applies to each culture's distinct music. The same bias appears in the other direction, because Indians regularly say they think Western music sounds out of tune and lacking expression. I don't think anybody brought that up as an issue though.
The difference, pertaining to this thread, is understanding music, versus merely aping riffs you learned from your heroes, with no regard to the underlying music and how things that fit, fit.