This exaggerates the problem. There is more preserved data about people than ever before, just like there was more preserved data last century than there was the previous century. There is simply vastly more data collected. I speculate that deleting 20% of this century's data would still leave an order of magnitude more data about people than was recorded last century.

I think future historians will look back in the same way we do now. We're horrified that people discarded, burned or reused records from every century in history, but technology allows us to record and preserve more every year.