A River Runs Through It (2021)

Both dramas have a main couple who are childhood friends, now in high school. In both dramas, the ML falls first and harbors a crush for a long time on the FL without her realizing.

Both dramas have a warm feel, a school setting, and an enemies/frenemies to lovers relationship between the main couple. FL likes someone else who only sees her as a friend. The ML in both seemingly picks on the FL who is annoyed by him, but when he starts to fall for her he falls hard and must try to get her to see him as more than a friend.

I won't say that it's exactly the same but the feels are very much similar. The communal relationship and how all characters are bounded with each other through friendship and a close bond.
Gen Z is more towards one's growth and about medicine and the romance part is not the main thing. However, in the other one romance and friendship is primary with the leads growth and how they find themselves through the process of teenage to maturity.

Both are set in the late 90s/early 2000s and the stories span over highschool, university and adulthood

Very different setting/plot but similarities in characters.

ML has a more unusual personality (more like a SML). It's not obvious at first who FL will end up with as she initially loves the other male character. FL is optimistic and very romantic.

School setting. Themes of nostalgia and growing up. Main couple support each other even before they're couple. Happy endings.