Sometimes true, but not always.
Can't really generalize, but yes I wish some kdrama's had more of a definitive endings.
CLOY is a ok example, I wish we would be more reassured though. But it's reality, and that's the best they can offer giving their situations.
Of course, having a child or being pregnant is the most definitive ending in rom-drama, isn't it?
I can think of many kdramas ending like that, Strong Woman Do Bong Soon for example.