I agree with you to an extent. I’m currently parent/guardian/disciplinarian transitioning to parent/friend/advisor. When children are on their own, sometimes the best thing is to allow them to make mistakes. It’s usually the quickest way to learn.
Yes, for some things you let them learn like that. When you’re watching them get ready to marry someone who is clearly going to screw them over, you do your best to open their eyes. Even then you can’t force anything on them, but at least you’ll know you tried. So will they when the S hits the fan.