He does not think mccandless is arrogant as many, especially in alaska, but he does seem that he was young, and had many of the common misperceptions of young, and claims that was really his main flaw. the implication of this passage is that if mccandless had survived, he likely would have ended up maturing learning to be close to people, to forgive flaws in those he loved, to interact with society and the world in less extreme ways. because of his death, which is certainly not any more deserved than if krakauer had on devil's thumb, he will never have that opportunity, and instead is blamed for his ignorance and hubris.