I hate to say this but CPS are staffed with, well, regular people. And regular people come with all sorts of biases and bad takes, some even with abusive tendencies and even history.
Add to that the extreme stress of that kind of work, and the poor conditions (bad pay, staff shortages, not enough training), and you far too often get a bunch of jaded people just ticking boxes without much concern for what they're looking at.
When we say defund the police, it's services like CPS we hope the money will go to instead, because they are in absolute dire need of it.