I totally get what you are saying and know how patronizing and annoying it can be when uninformed people think they have all the answers. But theres two sides to this. I was chronically depressed and somewhat suicidal as a kid and everyone I knew took the advice you are giving now. No one ever told me that exercise or eating healthy could have an affect on my mental health. That is not something that is inherently known unless we are taught. No one ever told me there was a way out of my depression so i felt helpless. As a result of this i like to forgive people for unsolicited advice because at least in my case, it’s a whole lot better than the alternative.