Compare it to physical health. For instance, everyone is advised to take regular tests (like blood tests). While things can still be improved a lot, this simple proactive measure helps detect many health problems before they cause serious damage.
For mental health, we don't do anything until the person is fed up with their struggles and maybe asks for professional help. Even then, in most cases we do not start with a "Triage" process. It took me a long time to even realize that there should be a mental health questionnaire, and ask my psychologist for it. We leave individuals to learn about mental health and take care of it, while there is not even a clear starting point for anyone who wants to learn.
Mental health problems, like viral infections, can be contagious. Unlike viral infections, one person with one mental health issue infects others with different types of mental health issues than the one they have. It is incredible how much happiness/productivity/economic value is lost to mental health issues that are manageable with our current knowledge.
If our collective goal for the society is to maximize a measure of overall happiness (which I think is a really decent goal), we need to have a better plan. Maybe advances in AI can bring proactive mental health monitoring to more people.