You just need to know your fundamentals, realism just makes it easier and faster to learn fundamentals than heavily stylized art. Although stylized art simplifies realism, you can miss crucial concepts like form.
You can draw any type of style with the knowledge of realism because you know how to break down or simplify fundamentals. Even if you're inaccurate with realism, your stylized art will improve tenfold. It's a jack of all trades type of thing.