The surface the great pyramids sat on was more level than we can achieve today with any of our advanced tools. Plus, for our purposes, that is excessive. It is also built on the golden ratio and has several interior examples of the same. It is perfection. It is also a model of the earth's dimensions. It also points to True North.

They knew stuff we can't account for at all. We know how it was built (with ancient tools and human labor), but not how it was made perfect.