Eh or just want to pretend to care about their health and the cost of being guilt free about it is a monthly vitamin D bottle.

In that case, the direction of causality is also reversed. Caring about health -> higher vitamin D, not the other way around, exemplifying my point. It's the caring about health that significantly reduces mortality, not the vitamin D, so implementing vitamin D supplementation as public policy to fight Covid-19 is unlikely to have an effect.