Ketamine treatment takes an hour, with virtually no chance of side effects, and you'll know if it works within a few hours. Even if it only works for a tiny percentage of depression sufferers, it should be first line treatment. As it is, it seems to work for a reasonably large percentage of people.
The reality is psychedelics may be the only meaningful medical treatment we actually have for depression.
[1] https://www.webmd.com/mental-health/news/20080227/antidepres...
[2] https://www.frontiersin.org/articles/10.3389/fpsyt.2019.0040...
a) Other ways of achieving peak experiences and senses of connectedness, wonder and awe, be that mindfulness/meditation, being out in nature, flow states, breathwork etc. which are more often accessible to everyone, for free and without needing to involve big pharma and may have less side effects, supported where necessary with the same complimentary (talking) therapies that run alongside the psychedelics.
b) Challenging some of the potential underlying causes, I'm not suggesting this will apply in all cases, but stress/burn-out, financial pressures, lack of meaning, lack of connectedness, pressure from social media, inequality etc.
Saying someone has "depression" is like saying someone has "a stomach ache". The stomach ache might be Crohn's, an ulcer, food poisoning, or the aftermath of too many hot wings. All would show at least a somewhat similar cluster of symptoms, different based on the person, but all "stomach ache". Imagine the same for depression, but we don't necessarily have the labels or causes pinned down very well.
There probably are many conditions under depression that we'll eventually have good diagnoses for and consistent treatments for, just not yet.
It's not a matter of "everybody is unique" but that the science and testing is quite primitive so far and only some of the distinctions and treatments have been worked out.
This imbalance affects serotonin and norepinephrine release.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8311508/
And this change is mediated by the immune system. Glutamate is now known as an immunomodulator.
"Depression" is just a label put on a cluster of symptoms to make diagnoses consistent across medical providers. It is definitely not a singular condition with one cause and a consistent treatment across patients. It is likely a multitude of conditions which will respond differently to many treatments.
Some people with a depression diagnosis will be very disappointed with ketamine treatment.