The circle of fifth, musical modes and any advanced form of transposition, alongside the basic theory involved in cords, their components and their succession are necessary for a musician. [1]
Technical proficiency does not make you a musician, just like being able to type really well doesn't make you a programmer if you can't...read code.
[1]: This may not apply for percussionists, but even there, playing together with others necessitates the same understanding.
Side note: it's per se