Except that it's actually really not. If we take my 5 year old son as a normal kid, a bowl of cereal for breakfast and then whatever random food they feed him for school lunch and we're already 2/3rds of the way to the goal. He snacks on fruit and stuff, but also on pretzel sticks and honey roasted peanuts and all sorts of other kind of junky things.
I make dinner from scratch very nearly every night, and my kid still falls into this 70% bucket! And so I really don't have a good idea about how to change that. Maybe make our own bread and have them have toast for breakfast every day? That's going to get old quick.