I think it is the fault of two parts. The Agency and the parents/politicans.
I think Agencies have the duty to protect kids but they only see the money they can make. The younger you are, the longer they can earn money with you and the easier you are to manipulate.
Then I see the fault by these who have to protect those minors. Their parents and the politicians. Parents should know that it is not good when children debut too early and politicians should pursue the protection of minors more. But most parents of such children only see the money, success and prestige they get from successful children and most politicians probably only see the financial and economic aspect Kpop groups have for the country.
In my country, for example, there is a law that minors are not allowed to perform after 10 pm.