A person's level of success will be a combination of nature and nurture. If a person's "nurture" score would be 2 out of 100, however, I'm not sure how much it matters whether their "nature" score would be 10 or 90. The highest levels of success would be out of reach for most people, no matter how well they were raised, but a person of average intelligence raised well could likely outperform a much more intelligent person who was raised badly.
Agreed.
IOW, we can degrade the intelligence of Einstein to a severely retarded level by a wide variety of methods.
But we have absolutely no idea how to produce Einstein-level intelligence in someone who is "naturally" of low or even moderately above-average intelligence.
Or, any idiot can make fish soup out of an aquarium. Nobody but God can make an aquarium out of fish soup.