I think you're probably right to a large degree. To paraphrase you're basically saying yes, there for sure is a very real genetic and environmental component, however if we simulate a reality where everyone runs their bodies and minds in an optimal manner we'd be far less likely to see all forms of disease including mental illness/psychiatric disorders.
The takeaway is if you're struggling with it, they are both important components that ought to be a part of a wholistic treatment plan.
I was watching something on Health Theory the other day and she psychiatrist being interviewed said they start with an elimination diet and the nutritionists have more success than the psychiatrists.
Food for thought.
Reducing the complexity of the bio-psycho-social model down to "exercise" and "eat better" isn't great.
Parent post is clear: get exercise, eat better, prevent mental illness.
But there is a percentage of the population that, even with correct diet, exercise, and general mental hygiene, are incapable of surmounting their mental health problems.
Everybody is different, and you can't really apply your personal anecdote to everyone who's suffered from depressive bouts or other mental health issues.
It's incredibly frustrating when people tell me I just need to eat right, or do yoga, or align my chakras and all my mental health problems will go away. It's borderline accusing me of being lazy or stupid for feeling and functioning the way I do.
Since then I've thought a fair amount about mental illness in general and have a few theories.
1) Diet. Get the right materials into your body so it can do with them what it needs to. Especially early in life while brain is still forming.
2) Exercise. Make sure your body can get sufficient blood / oxygen to all parts of the body so it can function properly.
3) The brain, IMO, should be viewed as a TOOL Sure it is already part of our body but this is why I think it's so overlooked as a perspective. If I decided to do some landscaping and needed an excavator, I would need to learn how to use it, and practice in order to become efficient and effective with my use of it. I think it's same with the brain. New circumstances come up all the time and sometimes the people who experience them have not trained their brains to deal with them in an effective / efficient way. There should be more focus on this sort of perspective / reflection / learning and perform these generally-applicable exercises early in life. Not just math, science, english, etc.
-- There is no doubt in my mind there are going to be SOME genetically relevant issues. But I would be surprised if, once this stuff gets fleshed out further, we don't come to realize most of it was preventable.