There

[… The only, yet the biggest flaw of the augmentation method; Brain death. The brain was the by far the single most fragile organ of the body. What other organs could survive; even the heart and the lungs, it could not even come close to surviving. Even this near-perfect solution when subjected to subjects caused brain death. The combination of mass brain-cell death and radiation was simply too lethal.

If the brain was left unenhanced while the rest of the body was evolved via this method, then the brain would die of extreme seizures anyway due to being stressed with metabolic processes that it was not evolved to withstand. It was not possible to evolve the rest of the body but not the brain.

No solution worked; it was absolutely not a viable form of human augmentation. This is why it's a dead-end for ordinary humans.

Ordinary humans, being the keyword. The goal of Project Apotheosis was to discover the breakthrough process to the Squire Realm.