You don't know anything about this kid. You definitely don't know that what they need in their life is discouragement. Don't conflate their childhood with yours.

If a 15 year old wanted to show me a project, and I wanted to help them understand what would improve it, I'd ask them questions and engage them in a Socratic process to lead them that direction.

I wouldn't tell them that their work was trash. That would either discourage them from doing more projects, showing their projects to me, or both.