I seem to read it says the kids are marginal because the decision to intervene or not depends on the investigator, not on the kid, parents or any determination

I seem to read it says the kids are marginal because the decision to intervene or not depends on the investigator, not on the kid, parents or any determination of abuse. They also point out that there is enormous variance in investigators so they say this covers almost all kids in care. That's what they say "marginal" means. Also: if the success rates for these kids are so low, then why intervene at all? Surely not doing anything is better than what this paper describes in terms of outcome. Or I should say: that's exactly what this paper says: no intervention is definitely the better option for the kid. And given that these kids end up in prison, it is the better option for both the victims of the crime that lands them in prison and for society that has to pay for it. So why intervene at all?