For the millions of those with 'psychiatric' disorders that are diagnosed using incredibly vague guidelines [0] -- do you ever feel tired? do you ever lose attention? do you ever feel really confident? -- using medications that do not have any observable and immediate symptomatic relief is not worth it. Many of these people have dysfunctions of cognitive processes or issues of their childhood that can be attacked in more conservative ways.
[0] http://www.mayoclinic.com/health/depression/DS00175/DSECTION...
I've been in first-hand contact with a fair number of doctors, psychiatrists, psychologists and their patients in Scandinavia, and I haven't seen the rampant prescription of drugs to treat vague diagnoses that you describe. If you're in psychotic and in a mental hospital, they'll prescribe drugs, ditto if you have a mood disorder that is severely affecting your functioning. If you have something that reminds of ME or a similar poorly-understood conditions, the meds usually remain off the table and other forms of therapy attempted. Regardless of the situation, if meds are attempted, it's an ongoing experiment to figure out if something works.
Psychiatry would benefit tremendously from a better understanding of brain chemistry. But you're suggeating that we shut down our interim attempts at improving the lives of patients who are suffering greatly today. Psychiatry uses our best guesses yet, and is the best option we have. Its similarities to quack medicine are superficial and incidental.
I like this idea. I have one question; in the meantime, while we spend the next five hundred years figuring out the brain (because as we already know, it is wildly complex and we know almost nothing about it), what do we do with the people who really need psychiatric help? Can we hang them out to dry, or would that be too cold?