Economic growth is based on very little more than consumption. There will be growth as long as demand is greater than production. The period after WWI is an excellent example of this, and the decades after WWII are pretty much the epitome. Most of what we called "the civilized world" was destroyed and it was a seller's market for pretty much anything. High demand for goods led to high demand for labor, leading to higher wages, leading to more demand for luxury goods... etc, etc, and it was more than two decades of whirlwind growth. Government(s) invested heavily in new technologies (or implementation of previously-unused earlier advances) because it a necessity to meet demand.
But during that period of mad growth those countries with destroyed infrastructures were rebuilt. As a very key point, they were rebuilt with the newest and most technologically advanced systems that existed, which catapulted them to the top of the list of producing countries, leap-frogging the countries that helped them rebuild. Post-WWII the USA (un)arguably led the pack, with Britain following close behind. But, at the end of the example, by the 1970s Germany, China, and Japan left them us both the proverbial dust.
Since then, well, not a lot of growth in demand overall. There's seldom been a time where a ready supply of laborers was not available, so there's been general wage-stagnation (yes, there have been a few key high-growth industries coming and going, but I'm speaking of things as a whole), and without wage growth exceeding the rise in cost of basic living expenses, a lower demand for luxury items. Not matching the post-war boom years should be no surprise at all.