The gameplay in CKII is a little strange. Most of your playtime is spent clicking through various menus and information lists, making decisions on events, occaisonally sending armies out to war but mainly just watching and letting the stories develop and the years roll by. Mechanically, crusader kings rewards, long term thinking, reading and synthesising a lot of information, using your systems understanding to turn that information into plans, following through with multiple plans at once on a micro and macro level and being able to adapt those plans and even mid to short term goals as opportunities come and go. If you can do those things well you'll be able to more consistently accomplish what you want to accomplish and drive the story in directions you want it to go, but so long as you're able to able to keep your head above water the game's fun at pretty much any skill and intensity level, and personally I even find it more fun when I'm not trying too hard to accomplish any one thing in particular.

I've written a lot, and I could write a lot more but I think I'll end it here.

Crusader Kings is a game about the stories of families and individuals, their quirks, their desires, their passions their loves and their losses, told against a backdrop of grand materialist history. I've spent a thousand hours delving deep into alternate what ifs and the stories of imaginary people in my computer and my mind, I've probably spent that again thinking about it. I don't regret my time spent with crusader kings and I'll probably play that again. If you love emergent stories from deeply complex systems, history and the stories of people in history and don't mind drawing them from numbers, cg portraits and little snippets of text I strongly recommend you give it a try. It's fun, it tends to slowly deepen both empathy and an intuitive materialist understanding of history in the people who play it, it's beautiful and its free.