So honestly I've been looking at your dropped list and I've noticed that you drop even shorter shows, so your dropping tendency seems to be not necessarily dependent on the length of the shows. Analyzing your list, I also realized that you tend to drop dramas after they lose their initial momentum, so typically past their climax. I generally lose interest in dramas at the same time you drop them; it's just that I get attached to the characters and don't always want to part with them, am too interested to know how it ends, or can predict how it ends, but still want to actually SEE the leads together or the mystery solved. You don't mind dropping the dramas even on the last episode. Are you sure you mind the fact that you tend to drop everything? Maybe it just doesn't matter to you that much. I don't like dropping dramas, so I will always force myself through the last 1-2 episodes. Maybe it's just not a big deal for you.
I would generally steer you away from shows that are considered too fluffy, or shows that don't have a strong plot (I'm looking at you, Descendants of the Sun). I know you say that cute and fluffy is what you tend to gravitate towards, but it doesn't seem like they genuinely hold your attention for long. I have a feeling you might drop some of the show you are currently watching, like What's Wrong with Secretary Kim, that follows a similar pattern to many shows you dropped. Have you ever tried more gripping crime dramas? Crime or mystery dramas tend to have stronger stories that don't fall apart even when the leads get together. Maybe try something like The Master's Sun? It's a mix of silly/fluffy with a mystery in the background. You may end up dropping it on the last 2 episodes, but you might enjoying the show nonetheless.
If you are not opposed to movie recommendations, I find Like for Likes to be pretty cute and concise, so you might enjoy it.