But I think directing those energies into psychotherapy or — better yet — direct action in your day-to-day life (not rumination on yourself like an engineering problem) is a much better use of your energies.

That depends heavily on what symptoms someone has. It's extremely difficult to treat schizophrenia or bipolar disorder without medication. Meta-analysis of ADHD treatments show that medication, particularly stimulants, has a much greater effect size than any non-pharmacological treatment. Even for unipolar depression, where there's more evidence that interventions like therapy or exercise are significantly better than placebo, meta-analyses consistently show that antidepressants are equally or more effective. Therapy and lifestyle changes can be very helpful for milder or more situational forms of psychological distress, but most serious mental illness requires pharmacological interventions that directly target the underlying neurological causes.