Doctors have no clue how the brain works, so any medicine they offer that effects the brain is useless at best and dangerous at worst. The only helpful psych drugs are the ones they won’t give you - Xanax, Adderall. If something is addictive, that means it actually works.
"Helpful" is relative. I had to get off of Adderall due to bad side effects like hair loss on my scalp/body, and increase in prostate/urinary infections (turns out stimulants have a link to this - Vyvanse also caused the same side effects for me, it's how we found out).
How does lack of understanding of the mechanism by which something works imply that it is useless at best? I do not think that follows and can think of many counterexamples.