I believe drawing skills are never innate: when someone is a natural, what they really have are remarkable observational skills and the ability to apply them in their case, through drawing (it could just as well have been espionage ). Drawing skills can be cultivated by anyone able to use their minds and hands. There are basically only two approaches to do this: theory (+practice) and observation (+studies).
Theory is a structured, organised approach, learning from someone more experienced who's laid it all out for us in a course, book or tutorial.
Observation is an organic, unpredictable approach, learning directly from the real world around us and gradually deriving principles from it.
Alone, they are both incomplete; trying to work with only one of them would be like trying to walk with one foot. Studying lays down a solid foundation, which remains abstract and limited until observation brings it to life with details and real-life application