I think you don't need to think about "realism" in the way you do... because what is "realism" anyway? If we think of it as trying to "get close to what it should look like", then if you are looking at a stylized object/image, then the "realism" here becomes stylization as well. So the ultimate goal is to be able to draw what you need it to look like, if you need to draw a thing that's looking like real, you are able to; or if you need to draw a thing that's stylized in such a way you imagined, you will then be able to as well. So the fundaments are really there so you know what your drawing would look like when you do it a certain way so after a lot of experience, you will then be able to choose what kind of movement to get you to your goal.

I've found that learning realism helps you with stylized drawings. And I've also found that practicing drawing stylized can help you with realistic drawings. So I would do at least some of both.

I've got a bit of a spiel about style, and how it relates to the "fundamentals" - which is, in a lot of ways, what you're asking about in regards to style vs. realism. You'll find it in its original context here: https://www.reddit.com/r/ArtFundamentals/comments/gpxkca/the_battle_with_style_vs_fundamentals/frpzxn1 but I'll paste it below as well. --- There's no battle between style and fundamentals. It's not an uncommon way people look at things, but it's not accurate. Instead, it's better to look at the concept of style as being a filter or a coloured lens through which one is looking at the world. The fundamentals are the world itself, specifically taking things that are three dimensional and capturing them - not hyper-accurately, but at least in a believable, tangible way - on the page. The fundamentals are about selling the illusion that what you're looking at in a drawing is real. Style is a series of choices an artist applies to their work. You can think of it as a recipe, or an algorithm. In that sense, it's not unlike how an instagram filter works. You've got an input (the actual thing being depicted), it goes through a series of choices, and out comes the final, stylized work. So when it comes to creating a style of your own, what you're doing is developing your own recipe, your own clear set of rules and choices that will govern the works you wish to produce in this style. The first thing you need to learn, therefore, is what are the recipes that others use? And really, what is a recipe? How do I apply it? You can do this by doing master studies - that is, studies that involve looking at another artist's work, and attempting to reproduce it specifically focusing on the stylistic choices they've made. You know how one might go about capturing something real at its most basic and most un-stylized (assuming you've got pretty solid fundamentals, which you should if you're worrying about style), and so you need to analyze how the artist got from that point to their end result, and decompile their algorithm. Find out what choices and rules they followed to achieve that cohesive look. Do this a lot. Do master studies of works you admire, do master studies of works that are in the totally opposite direction you'd like to go yourself. As you do so, you'll find little pieces, individual rules that will appeal to you, and as you gather these pieces, you'll be able to start experimenting on how those rules and choices can fit together into their own styles. These things will develop slowly - just like a chef testing out a new dish, they'll try things out, make tweaks, let things sit, scrap them entirely, and try again. And gradually you'll come to a style that has been tailored and engineered to suit what you want now. And you'll probably keep working on it even beyond that, eventually your tastes will change, and you'll find yourself desiring a new style altogether. And this is how you'll go about it again. But if you don't feel like you have a solid grasp on your fundamentals, on capturing things as they are (again, not hyper-realistic which is a style in and of itself), then you may want to strengthen those building blocks. That isn't to say you can't do master studies now, but that it helps a great deal when analyzing another artist's choices to have a good grasp on the raw material. --- So in this sense, understanding, say, how human faces are actually structured in 3D space will help immensely when it comes to understanding *why* other artists - say, manga, or cartoonists - choose to represent their faces in a particular fashion. It helps us understand why they're making the choices they are, and so in turn it allows us to better understand the choices we make. When we just attempt to create style without this bedrock, our choices become more arbitrary and less grounded. That said, if your art teacher is suggesting that you stop drawing whatever stylistic stuff you're drawing now - ungrounded and arbitrary as it may be - I staunchly disagree with that. I think there is a lot of benefit in balancing both areas, to draw the things you love most on one side, just for its own sake without stressing over whether or not it comes out well, or as you intend, and studying the fundamentals, reality, whatever you want to call it on the other side. Setting out separate periods of time for each will help you maintain balance. It's very easy to just delve completely into studies, and to lose one's sense of direction as a result.

I think you should learn what you are interested in learning ;) In saying that, if by ‘realism’ the teacher means to learn things like understanding form, perspective, anatomy, etc, then yes you should definitely learn these as you will be far more successful in stylizing later if you understand how things are constructed. Make sure stylization doesn’t become an excuse for not understanding. Ask your teacher why he/she thinks you should learn those things. Don’t stress about creating your own style, it’ll come over time. But do keep embedding the fundamentals in what you do! Hope that helped :)