Agree for the case of oncology. Disagree for psychiatry.

The evidence is mounting that vitamins may actually be just as good a treatment for most people with mild depression or other similar ailments vs SSRIs and other psychiatric drugs.

Sources:

SSRIs don't work better than placebos for mild to moderate depression Study https://www.ncbi.nlm.nih.gov/pubmed/18303940

Low B12 and Folic Acid are associated with Depression Study https://journals.sagepub.com/doi/abs/10.1177/026988110504889...

Vitamin D can treat seasonal depression Study https://europepmc.org/abstract/med/10888476

B-12 levels are associated with ability to recover from depression Study https://bmcpsychiatry.biomedcentral.com/articles/10.1186/147...

Magnesium helps to handle depression Study https://journals.plos.org/plosone/article?id=10.1371/journal...

While this is partially true, it is important to realize that most of these papers are talking about mild to moderate depression (not severe depression or any other mental illness). There is a ton of evidence that medication helps in more severe cases (https://www.psychiatrist.com/JCP/article/Pages/efficacy-ssri...) the main debate is whether depression meds are being over-prescribed in mild cases.