But this thread is, I believe, not looking at all games, but only TTRPGs. So while I am happy to say that compared to wargames in the 70s, D&D was not simulation-focused, I cannot say the same when we compare it to all TTRPGs. Yes, it uses abstraction, genre trappings and has gamist approaches -- I might argue that "hit points" are the most "modern" mechanic, as it's a purely gamist mechanic with minimal connection to realism(*). But the vast majority of the rules are in service of simulation, such as the selection on p13 of vol1 (I picked a paragraph at random) which explains in detail how relatives can inherit character's wealth, if they pay a 10% tax, but that if the original character returns they can recover their possessions, also paying 10%, in which case the player character must revert to being an NPC and start with a loyalty penalty of 0 to -6 ...
It is hard to argue that rules like this are aimed at being fun, or making the game flow easily. They're an attempt at simulation.