To me, there are two aspects to music theory: objective reality and taste.
Objective reality is the physical interaction between notes: universal truths independent of genre and culture. An octave is universal, as is the concept of a mode, of bars and beats and of strong and weak notes. Apart from ambient or abstract music, all styles of music are built on on these concepts.
Taste exists on two levels; community/cultural taste and personal taste.
Cultural taste is the prevailing taste of a particular era, region or school. Cultural taste defines genres and styles of music.
Personal taste allows a player to put their own stamp on a performance, whether interpreting an existing work or creating their own.
I believe that true understanding begins with a strong foundation in objective reality before studying a specific genre. This foundation makes it easier to understand how the characteristics of a particular genre are achieved.
If you understand the concept of modes, you can easily identify and learn a mode used in a particular era or culture. If you understand bars and beats, you can learn the time signature and characteristic rhythms of a particular musical style.