I did find this 2010 NY Times article:
Child Protective Services investigated more than three million cases of suspected child abuse in 2007, but a new study suggests that the investigations did little or nothing to improve the lives of those children. ...I agree that crimes should be investigated by police. We now have CPS, family courts, and colleges investigating and adjudicating criminal abuse of various sorts, and they are incompetent to do so. They do not respect the rights of the accused, or understand the unreliability of hearsay, or follow innocence until proven guilty.
In an editorial published with the study, starkly titled “Child Protective Services Has Outlived Its Usefulness,” Dr. Abraham B. Bergman suggests some essential changes: child abuse, because it is a crime, should be investigated by the police; public health nursing services should be the first to respond to concerns of child neglect; social workers should assess appropriate living situations and work with families to obtain services, and not be engaged in law enforcement. But Dr. Bergman, who is a pediatrician at the Harborview Medical Center in Seattle, expressed considerable skepticism that such changes would happen.
When the state decides that something is a crime, then accusations belong in the criminal justice system. It is evil to punish people who have not even been charged.
I also agree that CPS is not going to change, no matter how many times it is proved that they are ineffective at helping kids.