I Hear Your Voice (+1) is not only a vintage drama, I see it's on your Plan to Watch! I think it's a great ride, and fits your preference for a strong female lead. I get that you don't like amnesia, but I think the amnesia in IHYV is well done. But then, I love amnesia, so I may not be the best judge. However, one reason I like the way IHYV uses amnesia is that I like the way vintage kdramas excelled at hitting all the tropes extra hard. I mean, IHYV employs amnesia as a major plot point and exploits it to the hilt -- but it's not the only trope and far from the only major plot point.
What are your thoughts about Healer (+2)? I never get tired of talking about that drama... How did the first episode sit with you?
Here's a list I made of some older dramas I like: Five Kdramas 2011 and Older that I've Rewatched -- most of them work with your likes and dislikes, at least to some extent.
My Lovely Sam Soon has a super strong female lead. She's irrepressibly sassy and it's awesome to watch. There are also a few scenes with her sister and mom, and the apple didn't fall too far from the tree! No soft male lead here to begin with, but the ML is pretty funny for an asshat chaebol, and his soft side is eventually revealed. Also, the SFL is surprisingly multidimensional. (A note about terminal illness: She has survived a possibly terminal illness, and her survival chances look extremely good at the end of the drama.) As a rule, the way relationships are portrayed is contextualized and mature. I mean, the drama shows some unhealthy and some healthy relating, but clearly knows the difference. As far as embarrassing scenarios go, I think there are some, which is pretty much par for the course in 2005, but I don't remember them specifically, because I don't filter for that. However, one of the lovable and admirable things about Sam Soon is that she's uncrushable. She can take an embarrassing scenario in stride. Yes, there may be a moment of anger and humiliation, but she's reliably un-put-down-able. All in all, this drama is excellent food for the soul.
White Christmas definitely fulfills the morally grey characters requirement, and it's something like a murder/crime investigation, but there are no detectives figuring things out -- it's all down to the students and staff (marooned in an elite school in the snowy mountains during winter break) to save their own necks when the body count starts. This is a dark and twisty tale, and has no romance. The ending can be considered satisfying, as long as you're content that ... most of the developed characters survive and the antagonists are vanquished, and if you get some artistic satisfaction from witnessing everyone's dark side.
9 End 2 Outs is charming and funny and smart. I think it's mostly compatible with your likes and dislikes, too. I see you've seen both Coffee Prince and The Greatest Love.
There are a number of older kdramas on my watchlist, so if you have any questions about the ones I've seen, please ask. Feel free to DM me, too.
Bonus Korean romance film: Il Mare -- I'd watched an American remake of this, unaware of the original. When I finally saw Il Mare, I liked it better than the American version.
