Generally speaking people who need mental health help are going to be more easily discouraged by a negative interaction than the general population even if they can afford therapy in the first place. In the US at least there’s also a shortage of therapists, meaning you might have to wait a long time to see anyone at all. And in my experience there are a lot more bad therapists than good ones (though assholes of this level are probably rare).
Honestly if it were me I’d just save myself the trouble, read a book on CBT and get some antidepressants. But that doesn’t work for everyone.
You can’t really claim this without head to head trials comparing antidepressants with vitamin supplementation. There are too many variables that could differ between studies for it to be meaningful. The author also neglected to mention that the largest trial to date (VITAL-DEP) showed no difference over 5.3 years in depression with 2000 IU/day vitamin D supppementation. So while there may be something to this, more research is definitely needed.
I will put in a plug for iron deficiency as a contributor to depression though, which has much stronger evidence behind it. The medical community is just starting to come to grips with just how common it is, particularly in younger women.
https://ashpublications.org/hematology/article/2023/1/617/506479/Sex-lies-and-iron-deficiency-a-call-to-change