The problem you are pointing out is related to doctors' excessive eagerness to prescribe medicines, not any inherent flaw in the field of psychiatry. This is a problem with the culture among MDs in the US, it is not a global problem of psychiatry.

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.