This is a fun one. It's a common problem and honestly I've seen it a lot in even some very professional looking work. One really annoying issue is when you look at tutorials on the subject, they all do like "draw a bunch of shapes, now draw faces on them!" as if you're seriously gonna have a person in your fairly realistic comic whose face is a big tall rectangle and another who's a perfect circle. And worse, they tend to do it like only men and ugly/old women are allowed to have these weird shapes and all attractive characters, especially "sexy/cute girls" must have a standard oval face with the same "attractive" eyes, small thin nose and mouth.
A really good way to get better at drawing more varied faces is to draw portraits of real people. A lot of my early commissions that really helped me become a professional illustrator in the first place were actually manga style portraits, and one of the biggest jobs of my early career was touring the UK drawing manga-style portraits in a big tent to promote Dragon Quest IX (the first Dragon Quest game with a customisable main character appearance) for Nintendo and Square-Enix. I began to really start to notice things like the variety of eye shapes, eyebrow shape and height, nose width and nose bridge height and whether the nose tip points up or down, mouth width, lip fullness, ear shape etc.
I have an unusual face, and going to a uni where there were a lot of exchange students, was often assumed to be an exchange student myself even though I'm completely native british, because my more celtic/viking features were different from the more typically anglo-saxon looking people who made up most of the British students. So when I draw myself, I tend to reflect these very distinctive features. Narrow jaw, extremely narrow pointed nose, thin-lipped mouth, closely-grouped eyes-nose and mouth, almost elfin tall sticky-out ears, large, round blue eyes, very low and flat browline.
So to illustrate, here's a generic face I might draw on a background character I'm not thinking about much, versus how I'd draw my own face so that people would recognise "this is a drawing of Kate Holden":
The impression you get from the "generic lady" might be like... she looks fairly nice, inoffensive, works well as a background character, or maybe she'd be the protagonist's "best friend" in a down to earth Romance or slice of life. The impression of the portrait though is a much more specific character, probably one of those "quirky northern girl" comic relief characters in a British comedy movie or sitcom. The differences are subtle, but there are enough of them to give the face a sense of a distinctive person, even in a simple style and with neither being caricatured to a level where you wouldn't say they look cute.
This is how I approach all my characters. When I think of Subo it's not like "a handsome man with light brown skin", it's more like "a broad-faced Punjabi man with a prominent "roman" nose, gentle, expressive eyes, a wide smile and an unshaven jaw." And Jules and Urien, being siblings, both have the same , drooping, hooded eyes and flat eyebrows that makes them seem aloof and hard to read, and the same elegant, long face that evokes British royalty and milky pale skintone.
