See for example the largest study on CPS ever:
https://sci-hub.se/10.1257/aer.97.5.1583
Or it's popular summary "Troubled homes better than foster care":
https://usatoday30.usatoday.com/news/nation/2007-07-02-foste...
And let's not forget just how bad the reputation of CPS is where it comes to getting things wrong. Some studies claim that false accusations of child abuse, because there is no standard of proof for taking the kids away (only for locking up the perpetrators), that the false diagnoses and false accusations far outnumber the true ones.
And like anyone who's seen an orphanage (they don't like to be called that anymore) and half of all foster homes knows. Seeing damaged kids in those places is perfectly normal: those places damage kids. These places are not hospitals, where patients come in damaged and get fixed. These places damage kids, they don't fix them. They're more like the ragged pillow at the bottom of a half-pipe, a catchment area for broken bones, doing MUCH more to protect the reputation of the rest of the system than preventing or helping with injuries.
And the horrible thing about such places is that they effectively prevent the kids from having a future (they have extremely bad schools, no alternatives, limited learning materials, ...), but throw them out at 18 years (and please: 21 years or even something ridiculous like 45 years would NOT be better). Please stop pretending that after 10 years where crime (from stealing from other kids to dealing drugs) is the only way to get even a trivial little extra, no-one would remain clean.
That only happens in protected settings. And the sad truth is that even very bad parents still provide a very protected setting for kids.
Besides, these places, for the large majority they don't even try: treatment, though often the very reason kids get taken away, effectively doesn't happen in such places. Just 1 underpaid person, often without any qualifications, per 15 or 20 kids, and some director "handling" 20 groups. That's all.
https://en.wikipedia.org/wiki/Short_Term_12
https://en.wikipedia.org/wiki/System_Crasher
https://en.wikipedia.org/wiki/Instant_Family
Please note: "System Crasher" is the more realistic of these movies (especially "Instant Family" is extremely toned down, I can guarantee a kid doesn't just shout 2 sentences if they fear everything they have will be taken away. They fight and scream and cry and kick and ... for 2 months).
If you watch "System Crasher" 5 times you will even start to see WHAT is happening. This kid made a mistake. Mistake lead to reputation (ie. to school teacher at the very least pestering her), which escalated matters. Help, effectively meant using violence against the child and more and more fear. And of course, the kid never gets any say, and therefore never learns WHY one needs control over oneself. This escalates and escalates and escalates BECAUSE OF YOUTH SERVICES. If they refused to intervene in the beginning of the problem, the odds of it just blowing over were very, very high, as the kid and parents would be forced to self-regulate their relationship. That would have happened, and at that point there would no longer have been a problem. And, frankly, it's hard to argue that any tactic, other than what was done, was worse, given the outcome.