The issue is the physics. 60Hz doesn’t give you much time to do everything that needs to be calculated in the interval. All the objects can interact with one another so it’s not easily independent and parallelisable.
There’s still optimisations that can be made - disable physics and have only certain actions enable them for nearby objects, smaller physics range, fewer physics-enabled objects, etc. - but those all have drawbacks for the gameplay and realism too.
The issue is the physics. 60Hz doesn’t give you much time to do everything that needs to be calculated in the interval. All the objects can interact with one another so it’s not easily independent and parallelisable.
There’s still optimisations that can be made - disable physics and have only certain actions enable them for nearby objects, smaller physics range, fewer physics-enabled objects, etc. - but those all have drawbacks for the gameplay and realism too.