It seems like the minimal possible complexity of a sheet of fabric is always going to be higher than the minimal complexity of an engine simply because the phys

It seems like the minimal possible complexity of a sheet of fabric is always going to be higher than the minimal complexity of an engine simply because the physics of cloth are much harder to simulate accurate so you will never be able to find all the edge cases. Yes engines are initially more complex to build, but their minimum complexity once they are well understood should be lower -- even with the code needed to run them. You can't exact attach a debugger to the universe.