When this thread started, dudie mentioned that adult content (overt sexual content) was not the goal. A realistic view and a more serious plot were the things mentioned. Seems dudie and I are on the same quest! My list appears above in the string, but I will add one more really good discovery: Neighborhood Lawyer. No spoilers here, so feel free to read on. What I like about this drama is that it has adults doing adult things, non adults who are not trying too hard, pretty women with more than makeup to offer to the story, and plot twists and action scenes (plus dialogue) that don't insult my intelligence.
More often than not, kdrama creators churn out what the masses want to see, but the never ending supply of "youngish" dramas have a narrow range. Bad boy with money/good girl with no money, and other tropes that can be engaging but repetitive and eventually, not that interesting, one after another. It can be like a long drive on a straight flat road; you will want to encounter some turns and hills to keep the interest level up so the drive is not so one-dimensional and boring.
Seeking a little more from your kdama? Found one that is well crafted and worth your time all the way to the end? Don't keep it a secret! And check out Neighborhood Lawyer, subbed through Ep. 10 on 5/2.