There is a survivor bias here. It ignores cases where parents or kids failed to be 100% wise. When we are talking about a whole population, we are gonna have unwise or unluck cases when we "set kids loose".

Which may be fine, I don't know whether the tightened control of both parenting and kids nowadays is better. But we have to recognise the cost that comes with doing something like that. There is less risk-taking right now, and bad consequences seem to be taken harder, in a way human life is valued more, which imo part of the reason of the shift. The mentality "let kids make their own mistakes" can be fine, but that comes with accepting the possibilities of negative consequences these mistakes may cause, and I feel that the main issue is that we frown upon these consequences as society much more.