Sarcasm aside, we already have cures for these disorders. It's absolutely insulting to struggle for decades dealing with mental health problems, for the medical industry to hold the cure (which, incidentally, is also the key to allowing you to perform a lot of self-care steps which would improve your mental health), and to then be told that — no, you won't receive the cure because you're not our "ideal patient" so, instead, maybe try and bang your head against this self-help book that "cures" the disease. Obviously, the disease will be cured if you just try hard enough! Or if you just, idk, Cope With It.
The majority of self-help books exist to generate money and only end up reinforcing the point of view that if you are struggling with mental illness it must be your fault. They take the burden off the rotting, decrepit husk of capitalism and put the burden back on to you. "Oh, you have struggled every day of your life with X? Ah, but this self-help book solves X, so if it doesn't work that must be your fault and you need to struggle harder with the methods in the self-help book!"