I don't think this was intended as a general purpose argument against ever treating mood disorders. Rather, the parent comment is describing the fact that anxiety and depression are conflated with their corresponding disorders too often.
I can somewhat relate from experience: I went to a doctor for terrible trouble sleeping, to the point that it was affecting my physical health, that we assumed was caused by anxiety/depression[1]. I was pretty shocked at the rapidity with which she suggested going on antidepressants, particularly considering the tapering periods and the seriousness of the dependency and side effects that they cause.
I pushed back a little but it turns out that my doctor's cavalier attitude towards antidepressants isn't out of the norm: they're considered a "try it and see what happens" first line of defense, without trying to get a better sense of the patient's specific issues and whether therapy or other interventions, sans medication, would be a better fit (though I should note that the doctor recommended that I go to therapy if possible in conjunction).
Tangentially, this fits with a larger disillusionment I have with the medical system: a combination of screwy incentives, bad lines of communication between generalists and specialists, and a serious institutional/cultural case of a God complex leading to a lack of critical thinking means that I'm at the point where I pretty much keep anything a doctor tells me as just another unreliable information source, weighted more heavily perhaps than my layman's understanding of the research but on categorically the same level.
Ive seen the same disillusionment kick in among my doctor family members: in our conversations over the years, my sister and her husband have gone from a central case of said God complex to as much as telling me not to take doctors' advice without a heavy dose of skepticism.
I should note that I don't actually consider this a criticism of any individual physicians as much as the realities of the system. One of the biggest factors is that the average person showing up at the doctor is simultaneously incredibly dumb and incredibly confident in their understanding of the medical problem. It makes sense for doctors to be a somewhat heavy-handed and reductive, and once you build those habits into your institutions and pedagogy, it's hard to turn it off.
[1] Turns out it was the other way around: consistently not sleeping causes some pretty crappy psychological problems