The old-school, prevents rickets/400 in milk is enough, is what was taught for decades. The new-school, take a few thousand a day and it prevents winter respiratory infections is quite newer and less spread out.

Personally, I stopped having the vast majority of colds during the winter since starting D a decade ago. One or two colds since, and both were over in a day. Definitely a significant life improvement.

There are several dominant threads pushing back here on a professionally done study about the benefits. So no, the important information is not as widespread as you claim.