So, in other words... At best, a brain can be copied by imitating the electrical impulses in the brain, which can be done easily by sticking a needle into each and every brain cell and measuring their interactions, creating a digital model that the RAM of no computer in the world can hold. At worst, you also need to emulate an unknown number of chemical, biological and physical interactions that nobody is sure about.
That last line is the important bit—again assuming the herculean effort described would actually pan out. It was once blithely thought that DNA was a "blueprint" for an organism... then cloned animals, like CC the cat, started turning up radically different in appearance and character to their progenitor. All that other code once dismissed as "junk DNA" turned out to be latent instructions triggered by environmental factors—"epigenetic code." Odds are there's still a long way to go, more to learn.
We've at least dabbled with genetic engineering and medical treatments, while we know nothing about how mind ties in to matter. And yet certain futurists assure us that personalities can be "uploaded" into a computer memory.
Right.
Never say never, but until the science reaches the level of engineering, it's a little hard to promise a return on the investment. (Like commercial fusion power, which was only "10 years away" 50 years ago.)
Science Fiction is here to remind us that sometimes the impossible is precisely what happens and all the things people thought WOULD happen turn out to be red-herrings.