You know what else happened between 1970 and now? Increase of the labor force available to the developed world by around a factor of six to ten. When supply of something increases so dramatically, you should expect that the price paid for it does as well. This explains most of Krugman's observations. Robots aren't displacing human jobs - cheaper humans are displacing human jobs.
Now, I've read endless claims that due to technology, less people are working now than before. But when we look at what's going on, we see that such labor issues only exist in the developed world. And that a lot of that is because it's because it's so much harder to employ people and start new businesses than it used to be back in 1970. Rather than try to make their labor more competitive in the world, the developed world has turned around and made the problem worse while complaining about it and using that very problem as justification. For example, there are many direct effects that make hiring people more expensive, such as, minimum wage, shorter work week, and employer payments for various mandatory benefits.
And I see people continue to double down on this madness, for example, advocating shortening the work week even further. But that just means that people start to work more than one job to get by even to the point of getting paid "under the table" when the government regulation and taxation grows too much.
It's not just that these things aren't needed, but that their effect is opposite that which is intended.