I think he was un-subtley implying that this isn't Facebook. Not to be too harsh, but...well...it is true...
Yes, the focus is on his shoe, it is very under-exposed, and I think if you brightened it up the boy's skin would be a bit yellow.
In a shot like this the I think most fundamental rule (yes, because of the intent of images like this where it's obvious the intent was to get a n in-focus person I consider it a rule) is to make sure it's in focus. Some technical aspects are very subjective, but it's hard to convince someone that a portrait like this one is "good" when it's irreversibly blurry.
It induces many eye-rolls and snarky comments on this site if this is the case.