What does "simulate exactly" mean? To me, exact simulation is not so much an impossibility as a nonsensical concept. What subset of reality are we simulating, and to what degree of precision, and with what certainty? An "exact" precision as it relates to real world objects is not a well understood or defined concept. For integers, I can say there is exactly one Earth orbiting exactly one Sun, but I think that statement is riddled with assumption, inaccuracy and imprecision. For example, it is assumed that I am referring to the present Earth, but is the statement of when the statement is made or when it is heard? Even the word "is" is inexact.

Assuming you don't believe humans have any metaphysical component, then the only remaining question is whether there's some essential component to being human that depends on impossible-to-precisely-simulate portions of reality. Nothing we currently know of biology suggests that that would be true, as much as it continues being pursued by people who need there to be something mysterious about consciousness or brains.

In any case, a closely-but-not-perfectly-accurate simulation of a real human brain is still going to be human, unless you believe that someone becomes less human when they're experiencing some kind of cognitive decline, or a stroke, or other biological malfunctions. The point is, there is nothing essential to the having of a physical brain that creates the concept of consciousness or sense-of-self.