There are degrees of accuracy in simulation. I expect the effect of distant galaxies to be an extremely low-order impact and so I might reasonably exclude them.
Well, even in this case I doubt that you need to factor in the latest political scandal in the planet Zykonn-5. But even if you need to include every minute detail, it is still finite. IF the the totality of things that exist is infinite, infinity wins.
Of course it is also possible that we are alone in infinity, but that seems unlikely given what we know about evolutionary processes (perhaps even impossible given infinity, I'm not sure).