Surely looking at the value of goods and services we are able to produce with existing capital is precisely that which we should be measuring to determine whether it's enough?
It's easy to get money for really goofy projects with poor long term potential. Alot of motels and shopping centers are sustainable projects because of financial shenanigans where the developers are "harvesting" expenses to offset taxes for other projects and companies. Those schemes break down as the loans funding the properties shift from paying off interest to paying off principal. Airplanes are similar -- that's how you can fly to Europe on Norwegian Air for less than a bus ticket from NYC-Boston.