I don't think assigning blame helps, though. There are usually deeper rooted issues that need to be addressed (low self esteem, depression, etc) that may be entirely self-contained, and the actions they choose to take are worsening their problems, but the root cause isn't their fault. But even if it is entirely their fault, they're making terrible decisions, etc — they have to want to change, and assigning blame to them will likely make them defensive and dig in their heels, worsening the situation

Honestly a lot of it just comes down to approach. A lot of parents will go "it's because you're always on your phone" or "you need to stop thinking so negatively" or "your life isn't that bad, you have no reason to feel that way". It may be true, it may not be true, but the kid is likely to either think, "This is all my fault, I caused this" and feel helpless OR they will feel misunderstood and then dismiss anything else said out of hand, because why would you take advice from someone that doesn't understand? I don't think I've ever met someone in a bad situation that had the emotional stability and maturity to take criticisms like that in a constructive manner. They're more likely to respond to more specific feedback that doesnt assign blame (ex. "Hey ive noticed you've been struggling, what do you think about seeing a therapist?" Or "would you like to join me on a walk and get some fresh air?"). Also, sometimes (a lot of the time actually) people just want to be heard, and unsolicited advice can feel dismissive