Every RPG has shared fiction. That's the point of RPGing.
Here's a very simple resolution system for a RPG:
* When I declare an action for my PC I flip a coin. If it comes up head, I get to say what happens to my PC. If it comes up tails, the GM gets to say what happens to my PC.
Where is the simulation in that RPG system?
Have you ever played a RPG that is not D&D or a derivative? Have you played any of the games I identified as having no simulationist aspects: HeroWars, HeroQuest and HeroQuest revised; Maelstrom Storytelling; Marvel Heroic RP; In A Wicked Age; Agon; Cthulhu Dark; The Green Knight?
Let's just look at The Green Knight, which is easy to describe. Each PC has a Dishonour score. When you attempt an action, it must be classified as either honourable or dishonourable. If the action is honourable, it succeeds if you roll above your Dishonour, and if you succeed your Dishonour steps down while if you fail it steps up. If the action is dishonourable, it succeeds if you roll below your Dishonour, and your Dishonour steps up.
What is that simulating?
Presumably you've heard of Apocalypse World, which has spawned a whole family of RPGs (PbtA - "Powered by the Apocalypse"). Here is what Vincent Baker, the designer of AW, says on p 288: "The entire game design follows from “Narrativism: Story Now” by Ron Edwards." How is this consistent with "GNS" not being useful? It led to the most influential contemporary RPG design.