>For one, it seems to me you have to basically reject all of relativistic physics if you want to maintain a perspective on the universe where only the present moment exists. This is because the relativity of simultaneity tells us that there is no such thing as a universal present moment. How can only a single moment exist when there is no such thing as a single moment?

Humans do extremely poorly in relativistic environments because we tend to become expanding clouds of atoms at the energies needed to make relativity relevant to every day experience.

At the energies we can survive at a universal time is an extremely good approximation to your daily experience.