Notice the bait-and-switch equivocation. He conflates 'no meaningful growth' with 'does not meet expectations' with 'does not look like imaginary fantasy worlds.'
Aside from being dishonest, these beliefs are blindness and madness. Anyone who has been paying attention knows that our world has improved in an amazing number of ways in the past few decades, even ignoring computers and consumer electronics. Automobiles are far safer and more reliable. Most consumer goods are much cheaper and of better quality. The quality and variety of food has improved dramatically, and it is much easier to find specialty items and things suitable for restricted diets. There have been thousands of little improvements in health care, with clever gadgets that make things better for nurses and patients.
Some improvements may sound mundane, but they are important to people who use them, or important for our overall image of the world. Gear for hiking and backpacking is far better than it was 30, 20, or even 10 years ago, and it keeps getting better. Shoes and athletic equipment have improved in similar ways. The quality of print and paper used in magazines and books has gone up dramatically, and they tend to have a lot more content, even though the price has basically kept pace with inflation.
A lot of the change is hidden from consumers, but still makes our world a much better place. Safety and environmental regulations have transformed the world we live in.* We are polluting far less than we were 30 years ago, and the things we buy have far fewer dangerous chemicals. This makes things more expensive, but the environment is in a much better shape than it was. To pick one example, there is far less lead floating around our homes and streets poisoning our children, and this is probably a big factor in increased health and life expectancies.
So why do people believe that things are not getting better? Partly this is because the media loves to quote people like Theil and paint a picture of a world going nowhere. When people are prompted to think about their own life, they almost always say things are getting better. But when you prompt them with wildly inflated and unrealistic expectations, like personal robots and flying cars, you can fool them into thinking that things are not as good.
One of my favorite mantras is: "Never trust anyone who compares reality to an imaginary perfect world." Fraudsters of all kinds will use an image of a utopia to make people lose track of reality and become dissatisfied with their lives. If you use your own memory, and talk with your parents and grandparents, you will have a much better understanding of how the world has changed for the better.
The expectations we have are really amazing. In the past, people were pleasantly surprised by the progress that we take for granted. Now we seem disappointed if engineers do not hand us playthings suitable for gods. In the past, a television was considered a luxury, something that middle-class families would have to save up for. Now every 'poor' family complaining about how hard life is has several nice televisions and a monthly cable subscription. We demanded so much more out of life than our ancestors could ever dream possible, and complain when our standard of living grows at an exponential rate that is somewhat lower than we have been led to expect.
*I will often argue that there are much better ways we could regulate these things. But the fact that a command-and-control regulatory regime is incredibly inefficient and targeted taxes would be better does not change the fact that the environment is in much better shape as a result of the regulations.