probably you're not a well-versed reader in Japanese LN/WN. They have their own standard of what's average for a character, and sometimes they also have a defined characteristics of what's considered "average", without to the extent of labeling him/her apathetic.
Used to read them a lot of Japanese literature (translated into English), but I’ve really never been very into apathy in a hero — nor have I been particularly obsessed with appearances among protagonists.
It’s either a character trait or it’s not, and I most probably diverged on my reading material along that line (I’m not into solo leveling’s (granted: this is Korean, and so is SSS-class Suicide Hunter which is one of the most heartwarming stories I’ve ever had the pleasure to read — who cares about God Greed if he wasn’t so emotional and dare-I-say petulant; and he doesn’t lose that emotional aspect even as he matures as a person (and collects a half dozen wives… think he’s the first and only harem protagonist to not rub me completely the wrong way (who actually engages with his harem in such a manner))) main character after he starts losing his emotional strength — and I straight up dropped Parasyte for that reason (even though I am pretty sure that is a primary plot point)).
Ultimately, if the protagonist is stone cold: they are in desperate need of a personality infusion to keep it interesting for me.
I view it as likely that I simply stopped reading a whole lot of those stories, and the ones I did read didn’t really stick with me beyond the ick I associate with them — to the point I didn’t really recognise average-looking protagonist as valid. It is quite the surprise to find out it is quite the opposite :)