Isn't there some valid probability in stating humans should likely eat what they've adapted to over hundreds of thousands of years?

And humans have been using medicine for thousands of years, which have an intrinsic property of being good for us -- thus vaccines are just an extension of this.

I'm all for resisting fallacies but this hypertechnical idea that natural vs unnatural is completely irrelevant due to a few exceptions is counterproductive. It's practical and beneficial for the average person to view natural things as better.