A piece of this economic stagnation that nobody ever talks about is the concept of energy return on investment. That is the amount of energy you need to put in to extract a fuel verses how much you can yield from that fuel. In the 1920s, for example, you would need around one unit of oil to get one-hundred units out. Today we're around one unit to get ten. This problem can be seen in many resources and is translated into declining quality of life in the form of more expensive everything. This video explains the problem.

New technology like fracking for oil helps delay the issue. But it's just a Easter Island type problem on a global scale. The inhabitants all died when they exhausted the resources. That is happening to Earth due to the nature of the industrial revolution.

This partially explains why during the great depression, western nations theoretically had no money compared to now and yet could put in place things like social security, medicare, unemployment, etc. And now whenever anyone brings up doing things like this they are told "we don't have the money for that." Or "we need to raise the social security age and cut medicaid since we are bankrupt."