I don't think simpler is the correct word, but more understandable.
As in, given an end state you can trace back the series of events and actions to how you got there. So for a character in a movie or in a story or in a DND campaign, you can look at where they're at, and then trace back and find out how they got there. Even in pretty complicated movies, because the audience needs to know and understand what's going on.
But people aren't like that generally, because you don't have enough knowledge typically and you don't necessarily know why people are the way they are. Feelings can come up for no reason, or for a reason you can't identify. They can even come 40 years ago, perhaps their inception when you were a baby.
You talk about "excess of thinking" and complexity, and I think this sort of points to that.
Movies, characters, DND can be rationalized. Humans, their feelings, and their actions, often can't. Not because they're more complex, but because people aren't rationale beings. Most people can't pinpoint where their own feelings stem from and it takes years of therapy to find that out - let alone the feelings of others. And, even worse, the feelings of those you don't know well.