Simulation is another matter. Simulation by its nature cuts corners. Otherwise why bother? The challenge of the game of deciding if our universe is a simulation is finding a way to spot the shortcuts taken in the simulation.
Neither I nor Occam assert that the universe is in its simplest possible form, Occam suggests that is the likeliest assumption, and so far he's been on the money. Reasoning from other assumptions would require extraordinary evidence.
People do use Occam's Razor to reason about the nature of the universe. Here is a reference to an argument that the Bohm-DeBroglie interpretation of quantum physics is incorrect because Occam's Razor: [1]
[1] https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory...