so it writes teen characters, but then puts them in INCREDIBLY adult situations. It’s easy to either overlook or ignore this character being a high school student when they’re a badass knight, or princess in some other universe, ya know?

Exactly this. This is what bothers me in general about people clutching pearls over characters ages. In general, the only way many of these characters actually resemble teenagers or children is that they're small, or that the creator happens to be explicit about their age. But otherwise they're characters created by adults, voiced by adults, written by adults, and otherwise in general portrayed very adult.