I think Elon Musk is a prime example of why this guy is probably wrong. Elon Musk needed quite some time and money to organise sending a rocket successfully into space. He hired a lot of people for their expertise, because he didn't know everything and didn't have the time to learn everything by himself, let alone build it.
If an Elon Musk were to attack this problem in the way such a problem needs to be attacked, then things would be interesting. Humans are more complex than rockets.
He's not building a human though. He's building food. Modern rocketry has been around for about a century, and food has been with us since the beginning. I don't see why it would be that complex. Like pg said, the top comment for every new product posted on HN is always something dismissive that doesn't really add to the discussion, and this thread is no exception.
Human females contain an environment in which an organism, after being bootstrapped, can assemble itself into a human using mostly food as input. I would argue that building the correct input for that environment and process is exactly as complex as building a human.
If an Elon Musk were to attack this problem in the way such a problem needs to be attacked, then things would be interesting. Humans are more complex than rockets.