The issue is that this only works in some cases where the root cause is well understood. "Bacterial infection, give this antibiotic which kills the bacteria".

The issue is that this only works in some cases where the root cause is well understood. "Bacterial infection, give this antibiotic which kills the bacteria". In other cases, the root cause of an issue is obscured under a complex system. The current cutting-edge pharmacodynamics understanding of depression is that "it is an issue with serotonin/norepinephrine/dopamine/etc... except sometimes it isn't". This leads to situations where you have psychiatrists prescribing a few SSRIs to treat someone's depression, except it sometimes doesn't work with the patient and they're not sure why, in which case they try atypical antipsychotics, except that sometimes doesn't work and they're not sure why, so they try NDRIs, which sometimes doesn't work, so they try MAOIs, except sometimes that doesn't work, in which case they try tricyclics, unless that doesn't work... you get the idea. This "guess and check" method is currently the legitimate scientific (not quackery) method that psychiatrists are working with. Unfortunately, since fields such as brain chemistry is immensely complex, "it works if you use it on the right patient" is still a legitimate scientific response in many situations.