I think the creators of Korean dramas are aware of the issue - the last one I watched was The Glory, which seemed to go out of its way to make its characters visually distinctive.
For me, I have to stop myself blanking it when I hear a name from unfamiliar language, and instead of thinking “Well I’ll never remember that”, force myself to take note, that’s she’s “Lee Sa-ra” and he’s “Jeon Jae-joon”, etc. I find it useful to pause the screen once in a while, to actually make sure I know who’s who, and what their motivations are.