It's all about empathy and emotions.
There's a video called LOST In 3 Minutes, where a man explains in a simple and straightforward way what Lost was about. However, at the end he says:
For me Lost isn't a show that's about the story, it's about how the story is told.
Have you ever cried because of a movie? If you haven't, I would personally suggest:
- ET (1982, Steven Spielberg);
- The Iron Giant (1999, Brad Bird);
- Your Name. (2016, Makoto Shinkai);
A well-crafted emotional scene will move you, even if you already know what is going to happen. Facts and feelings are two entirely different things. You remember facts, but you experience feelings. That's what makes them so powerful.
In short, when writing, consider the emotional impact of your words. By this I don't mean you should turn everything into a melodrama. I mean that your audience should engage with your characters, your world, on an emotional level too. The worst sin art can do is leave someone indifferent and unaffected.
Don't worry about having unlikable characters: Travis Bickle from Taxi Driver and Tony Montana from Scarface are far from being saints, but you can still relate to them. You can see where they come from, what choices they make, and what they become. Even if you don't agree with their actions, you can still empathize with them (understand why they're doing it), and you may even identify with them. I could relate to Travis' self-inflicted loneliness, and Tony's jealousy, for example.
That's what makes you want to come back, or stick around, even if you already know what's going to happen: wanting to know what those characters are going to feel, and how you're going to feel about them.
For example, if you have a man whose death is certain, what are his genuine feelings, leading up to it? I think it would be hard not to find the thoughts of a man who is going to die interesting. We don't know much about death, which means that as much as we are scared of it, we are also fascinated by it, and eager to know more, anything that can help us understand it.