The past has passed--except for those who grew up in our own version of the Modern World in the 50's and 60's.
We know how it was because we lived there. Those who came after us can only reassemble mostly faulty portrayals by others who weren't really there.
Think about a time 20 years before you were born and your memories are always wrong. It's pastiche made up of spare parts found in the city dump of pop culture.
I wish I could do it over again knowing what I know now. I fretted over too many useless things and ignored too many important ones.