imo its not the rules of reality that specifically matter in a game; its that there are rules at all, and that they're interesting ones. Emulating reality is just an "easy" way to achieve that. Games are inherently a challenge to learn, understand, and best an instantiated mini-universe.

when the universe follows simply-governed rules, then of course there's little for the player to do; he wins by understanding, and understanding simple things is, well, simple.

And ofc, the internal rules can very well be trivial to implement. Its the rules to from the players viewpoint that matter. And vice versa; the engine could be infinitely complex, but if all it does is spawn the same mountain repeatedly, then there's not much left once the player bests the first.