This is a complicated issue, because I've seen both sides in my time as an illustrator, running manga workshops and interacting with a lot of professional illustrators with a manga influence.
In some cases, an artist insistently drawing in a manga style (or really, any heavily stylised drawing style where there are widely agreed on stylistic shortcuts or visual metaphors that can be simply copied) is robbing themselves of artistic growth in favour of copying a style without true understanding of WHY they're drawing things a certain way for quick praise. In other cases, however, I've seen actually quite inventive and eager artists with unique hybrid styles that just draw some inspiration from manga, particularly young women, pushed to conform to their teacher's preferences for "more serious" drawing (often in a style more appealing to a male audience), and saddled with a guilt around drawing anything that's cute or accessible that ultimately harms their careers as they desperately try to impress the industry with serious, intense, artsy work that in illustration is rarely desired outside of a small circle of academia while there's actually more demand for illustration that's simple and pleasant.
If your class is Fine Art, then I need to be clear: no, you straight up should not be insistently producing illustration. Manga is illustration. If you want to draw manga all the time and to do so to sincerely tell stories, not as like... single pieces that are making some kind of commentary deconstructing pop culture, you want to be an illustrator, not a fine artist.
If you're trying to be an illustrator, and you want to specialise in manga art, then okay. Yeah, I said it! Okay! There's actually more demand for manga style illustration than there is for the painty fine artsy weird stuff a lot of illustration lecturers try to push their students towards.... BUT. There is a massive but here... Almost nobody I know who specialises in manga style or manga influenced work only draws that way. You gotta be able to flex or you will make it almost impossible for yourself to make a career. Here are some examples of my biggest gigs as an illustrator:
Doctor Who: The Women Who Lived book:
Nowhere near as manga as work I do when drawing for myself. In fact, there are a lot of artists who normally draw in a manga style in this book, which features a lot of female British illustrators known for drawing manga style or manga influenced work: Naniiebim, Sonia Leong, Emma Viecelli - All of us drew less manga style than usual because we knew the BBC wanted to capture the likenesses of the actors from the series, and that people reading the book would mostly be fans of Doctor Who; not necessarily weebs.
Mascots for Serverless Days tech conference:
Tech events LOVE this kind of cute, simple cartoon work. It's accessible, and unlike manga, which tends to vary from person to person as either "love it!" or "UGH!", most people like this style. They made pin badges of these mascots, and even my mum, who hates manga, and my hipster fiance will happily wear those badges on clothes and bags.
If I just insisted on always drawing manga style, I'd have never got these jobs. Big jobs for big clients and the kind of money that allows a person to make a living as an illustrator. Having a flexible style means learning to draw without relying on a specific pipeline or set of stylistic crutches. Doing that requires study of anatomy, line quality, colour theory, different approaches to stylisation, rendering in different artistic media, perspective... all that good stuff... which happens to also be pretty handy for developing your own unique approach to manga too!
When I would run manga workshops, I always tried to focus on teaching people first to think about more broadly applicable lessons. How to break down a complex shape like a body into simpler shapes in order to block out poses. How to think about simplifying down to an appealing style... But there'd always be at least one person, usually sat off in a corner, who didn't want to learn. They just wanted to copy drawings from manga, or to follow the same guidelines for drawing a pretty manga girl face from a how to draw book over and over again, because that's easy.
I see a lot of very generic, derivative manga style comics on Tapas. Every panel composition is something you've seen a thousand times before in a thousand forgettable C-tier manga, any time there's an expression, there's use of visual metaphors like sweatdrops to prop up a lack of effort into really depicting an embarrassed face and bodylanguage. Like, sure, it doesn't look bad, and it'll probably get an audience because it looks polished and familiar, but it'll never be great, because at the end of the day, it's just a poor copy of somebody else's work, lacking the emotional punch and dynamism of an artist who is really expressing something in their own way from observation of life. The best mangaka largely don't have generic looking work. You wouldn't mix up Arakawa, Oda, Toriyama, Yazawa or Araki with anyone else, because their styles aren't just generic manga, they're unique to them; immediately recognisable in a way that only happens when somebody builds their style from the ground up with study and varied influences. Even if you literally only ever draw manga, to be an A-tier manga artist, not just some forgettable jobber, you need to study other things.