This book posits that humans have core capacities to manage themselves, and that while many societal practices may atrophy those capacities, they do not go away. The author also believes that everyone has an Essence that is trying to express itself--though how it expresses varies with maturity and in different contexts/cultures. Some Essences are more sensitive to toxic practices in dysfunctional contexts than are others. Being allowed to manage one's self and work toward the goal of expressing one's Essence (reason for being here) is more efficient, healthier, and better for the bottom line, customers and the larger needs of the world. Relying on feedback systems based on other people's input creates work for those people and weakens recipients' core capacities to self-reflect and self-direct. Performance appraisals narrow employees' focus down to how co-workers perceive them and take focus away from what they and the company are trying to contribute to the world.
Many students of psychology or of A Course In Miracles will already relate to Sanford's claim that feedback is inevitably and unavoidably projection, which means it tells a lot more about the person giving the feedback than about the person they are supposedly assessing. Feedback is also distorted. Some of Sanford's examples seem to be drawn from consulting work; one stuck me as tragic in the classical sense, where a manager whose team outperformed most other teams was driven out by feedback that criticized the very thing that made him different from other managers and had created his success, as evidenced by poor performance of his team after he left (tragic in that his best quality was characterized as a flaw by those all around him).
Overall the book makes a good argument against feedback and other toxic practices that are alluded to, while not being sufficient information in itself to turn a culture around into a developmental culture. The systemic frameworks and hard reflective questions are not actually detailed, so the book seems in many ways like an ad for the author's consulting services and other books. I do think Design Thinking and Agile methods like Scrum would both have a lot to offer in terms of psychologically safe self-management that chooses to do valuable work of benefit to customers.