"Happiness Economics" sounds a bit like lefty pseudo-science to me so you'll have to forgive me for not buying into that.
Productivity is down in developed nations due to globalisation and the shifting of production into the developing or 3rd world. It has been going on for decades now and it is the reason for stagnation in the living wage in the West. Look at global productivity rather than a subset of it and you should see a better trend.
Plus, we are suffering from the increased "Financialisation" of our economies which is not helping productivity OR wages in the developed world. We've actually had anaemic growth since the GFC and have never truly recovered.
Calling something "lefty pseudo-science" isn't an argument - they use logical reasoning and support it with empirical data. For sure, developing countries productivity growth is much higher. But globalisation should bring increasing productivity - more options for trade. Not sure about financialisation although I'd lean towards agreeing with you. This guy puts the technology point quite well - https://www.amazon.co.uk/Summary-Rise-Fall-American-Growth/dp/1683780485/ref=sr_1_1?s=books&ie=UTF8&qid=1515180995&sr=1-1&keywords=rise+and+fall+of+american+growth
But intuitively, early twentieth century had incredible changes compare the 21st century invention of a smartphone with the invention of phones and telecommunication. Before the phone, people lived in a world confined to their village or town.News spread very slowly. A smartphone is an improvement over a phone, but it's not a completely different uphaul of society (obviously quite hard to define what an "uphaul of society" is though!).