It is literally the job of parents to arrange their childrens' lives. For example parents have to provide food, shelter, clothing, health care, education, entertainment, and emotional support to children. They also have to create a schedule to fit all that into each day, plus leave sufficient time for sleeping (kids need a lot of sleep).
The question is, how best to do all that?
You're right that parenting is difficult and nuanced. You're wrong to use that as an excuse to tune out experts who study child development for a living.
The difficulty and complexity of being a good parent is a reason to seek information and input, not reject it.
The question to ask is whether the book is just shaping your understanding of what the child tells you or whether you are now listening more to the book than to the child. The books I have seen all argue for their preferred theory of what's good for children. Preferences of children (whether expressed eloquently or through tantrums or just inferred by the parent) are never considered. This book seems to be no exception.
The question is, how best to do all that?
You're right that parenting is difficult and nuanced. You're wrong to use that as an excuse to tune out experts who study child development for a living.
The difficulty and complexity of being a good parent is a reason to seek information and input, not reject it.