I am not arguing against that. I argue that correcting this deficiency is not in the competence of people who are not medical professionals no matter how many articles they've read on the front page of HN about vit. D.
You are speaking nonsense and lies, considering anyone can get themselves tested. Visiting a doctor is not needed for it.
Doctors are in fact notoriously bad when it comes to vitamin D. None of the docs that I have ever visited eagerly tested my level. I always had to beg for a test. Moreover, none of them ever helped me optimize my level. It is tragically dangerous and harmful to rely on them for it.
You can very much overdose on Vit D. I suspect your risk tolerance is different than mine.