I have put a ton of hours into Crusader Kings III. It is less complicated than other grand strategy games, but the real fun is leaning into the generative story aspect and roleplaying as your family throughout generations.

It also has a great modding scene, as most of the game logic is defined in text files in a custom scripting language. If you learn a bit about the language it is very easy to get into, you can just edit files in a text editor and the game will automatically live reload and apply your changes.