That's a huge stretch. You could say that for most illnesses we have some idea how to reduce the risk, but there is still an overwhelming amount of luck involved.
(And that's before we even get into the luck-based factors that make lower-risk behaviours harder or easier for different people.)
Those are all trivially avoided.
Most of what I need doctors or other quasi-medical professionals to assist with is congenital or... wait for it... sports related. Turns out that 'get plenty of exercise' doesn't automatically fix everything. And it's harder to manage 'plenty' once you get older and everything fucking hurts.
So many of my older friends have informed me that my definition of 'everything hurts' is adorable that I'm starting to worry that they're right when they tell me that I haven't seen anything yet.
Now I'm 40, and this Sunday night I start seeing double when gazing above the horizon. After finding an opthalmologist who would see me immediately and getting MRIs and blood tests, it is diagnosed as idiopathic optical inflammatory syndrome and mostly treatable (although it tends to come back). I suppose I should be happy it's not a tumour in my brain.
Ah youth, wasted on the young.
When I report all's well in fifteen you'll just claim it's good genetics.
There are things in my life that have gone spectacularly well, and some that have gone pretty badly. So here’s me in the middle, with a pretty okay life that others envy, but the bootstraps people look down on.
> The vast majority (85%) of cases of lung cancer are due to long-term tobacco smoking.[4] About 10–15% of cases occur in people who have never smoked.[14] These cases are often caused by a combination of genetic factors and exposure to radon gas, asbestos, second-hand smoke, or other forms of air pollution.
So even for lung cancer, a significant minority of sufferers have never smoked. Genetic factors are obviously out of one's control, and the others mentioned can be pretty damn hard to avoid, especially if you're poor and/or born in the wrong place.
Okay, but that isn't fully within anyone's control either, and you're still ignoring the diseases that are predominantly genetic, the ones that happen more or less randomly as far as we can tell, the ones caused by environmental factors in childhood, and all the people who get a 'preventable' disease despite doing what they could do avoid it.
I'll stop arguing after this though, I think we're either talking past each other about the definitions of 'vast majority' and 'preventable', or having an unspoken argument about the general attitude we should adopt toward people with health problems, or at a factual impasse that we can both google our way around if we care enough.