CPS is so competent here in Florida that they leave a 5 year old girl in the custody of a man they were told would harm her, giving him the opportunity to throw her off a bridge, killing her.
Anecdotes are not data. You cannot expect perfection - if you have a sufficiently large organisation, someone will fuck up sometimes.The question is if the organisation is doing an ok job overall, and if it there are ways to address errors of judgement.
Also, there is the perennial problem of adequate funding. A decent service of any kind is not free, nor usually cheap. Either we need to pay sufficient taxes, or we must do without certain services provided by the state (and/or live with crappy services). If a CPS worker has to handle 8 cases per day, they can spend a grand total of one hour per case (assuming no overhead -ha!) - and if a team of to spends half a day on one visit, that means the other 15 cases get only about half an hour.
We can whine one way or the other, but whining both ways (less taxes and more/better services) is not a sign of much maturity.