"Poorly" is relative. Most Westerners suffer no deficiencies, and are unhealthy more from a lack of activity and excess intake. This turns people mystical about their food, as if finding the magic elixir will cure lifestyle issues (such as the current hysterics about carbs: The Japanese get 70%+ of their calories from very simple carbs -- white rice, which is of a nutrition profile closely related to table sugar -- and they have marginal obesity and excellent health profiles. They just eat less of it and maintain active lives).

There is the paradox that the US is one of the least healthy people's, yet one of the most absolutely obsessed about their food.

A Big Mac has an enormously complex nutritional profile, as hard as that may be to imagine. An egg and a slice of bread is a superfood. Both have been maligned because of excess or sedentary lifestyles, but either in moderation can be an ideal part of your diet.

Nonetheless, I dislike the linked article: It attacks Soylent mostly from a defensive, elitist attitude that tries to hold information freedom as some sort of anti-intellectualism. While there are legitimate complaints about Soylent (and I don't think "everyone is different!" is a good approach), it seems like the creator(s) are trying to find the relevant information, and trying to use the accumulated knowledge of nutritionist. Just because they didn't classically train as a nutritionist does not invalidate their work.