Agreed - I do believe that Frequentist methods are primitive compared to modern machine learning.

Also, I don't even have a strong opinion on whether a few years of vit D supplementation in the elderly is going to make a big difference in many health outcomes like cancer risk - the correct comparison is between a lifetime of adequate vit D levels vs a lifetime of inadequacy. I don't suspect that correcting it late in life is going to avoid most of the cancer risk.