It’s mostly an academic understanding. I’ve read some rules systems that I’m given to understand are narrativist, and I think they would be fun to play, in a different way than D&D 5e is fun to play, but haven’t had occasion to do so. I have played a lot of D&D 4e, which is generally praised for supporting narrativist play pretty well, and loved it. But, in terms of what would need to change in 5e to support narrativist play? I mean, the basic gameplay structure isn’t really set up for it. You’d need to re-structure the conversation of the game around dramatic conflict rather than environmental interaction. 4e did this by building everything around the encounter as the nexus of the gameplay, and provided a structure for non-combat encounters that was focused on consequence resolution rather than task resolution. You could incorporate some of these ideas into 5e, but I think the result would just be a bad imitation of 4e. And, honestly, there are other, better systems out there for narrativist play anyway.