I've talked about this before and I think it's a bit of a misdirection to talk about this as the blank spaces in the system as if they are more fun.
The real question is what you are trying to simulate? And a narrativist game, for the most common sense understanding of what it means to be a narrativist game, is a game that is trying to simulate being in and partaking in a story.
And the trouble that "nar" games run into is that nar mechanics are typically terrible for actually doing that.
The fundamental issue (in this specific case) is that in a tabletop RPG what we are really doing is sitting together and talking. RPGs are a conversational game. And it turns out that conversation is a very bad simulation of things like combat. If we want to simulate combat whether taking place in the framework of a story or not, we need a lot of props and algorithms to generate that other than conversation.
But, if we are wanting to simulate a social encounter, well, do you know what simulates a social encounter really well? A conversation. And it turns out that if you are simulating dialogue and social interaction, that more mechanics makes that simulation feel less real compared to less mechanics.
And this is particularly true from the perspective of an observer, and well, he's doing productions designed to be observed.
The truth is that it's not enough for the rules to have an intention. The actual outcome of the rules matters. And most "nar" rules hitherto aren't very good at creating story.