Yeah, I work professionally as a gpu/graphics programmer and even I have trouble sometimes wrapping my head around some of the fancy shadertoy one-liners. Most of the stuff I work with is conceptually much more simple. The math if any is all generally really straightforward and derived from a handful of commonly used algorithms or PBR models. The more common work is performance tuning and scaling across multiple architectures/platforms. You might run into this stuff more if working with SDFs though.