Demand has always been around since the dawn of time. Yet most of the world's economic growth has occurred in the past 200 years, which is when our understanding of specialization began to take hold and be incorporated into the productive process. There has always been demand. There has not always been innovation large and adaptive enough to drive significant and widespread wealth creation and distribution.
Demand without purchasing power has existed from the dawn of time. What has changed in the last 200 years is of course capacity as you say, but capacity is useless unless it it is preceded by excess purchasing power.
Which is why a large % of the world has only marginally participated in the consumer economy.
Innovation drives industry, but it doesn't drive the economy. The economy is fueled by currency. As is evident by contrasting the wealthiest and poorest nations of the world in a globalized market. The same products are available to everybody, products of the same innovation. Demand is universal, but purchasing power is not equally distributed and extremely disparate results are evident as a result of purchasing power inequality.
The same is equally obvious when looking at consumption within individual stratified nations. Demand universal, supply universal, purchasing power and consumption not equal.
Purchasing power(currency) coupled with demand is the engine of commerce.
The disparities in income around the world are a function of productivity. American workers are extremely productive and are paid as such. Congolese workers are much less productive (as defined by output per time worked), and are paid much less. Countries that have been poor and become relatively well off - particularly those in Asia - have done so through technology transfer.
I said earlier that all economic growth is a function of innovation and productivity growth. That's not true. All
real per capita economic growth is a function of innovation and productivity growth. This can be demonstrated with a simple example. If one earns $20 and spends $10 on food and $10 on clothes, if someone creates a new way of making those same clothes for half the cost, the consumer now spends $10 on food, $5 on clothes and now has an extra $5 to spend in the economy, which is spent elsewhere on other goods or saved, which increases economic growth.
Demand does not operate independently in a vacuum. What was the demand for online gaming 50 years ago? What is the demand for moon vacations today? Demand, independently, is theoretically unlimited, and doesn't tell us much about economics.
The best definition of economics I ever heard was from my first economics class in high school, with the teacher defining economics as "the study of the allocation of scarce resources to meet unlimited wants and needs." "Wants and needs" is demand. "I demand to have sex with Victoria's Secret supermodels every day." Yeah, well, who doesn't? But on my opportunity set, that is unlikely to happen. People can demand cars that cost $5, but that is irrelevant since it costs much more to make a car.
Demand is a function of income, which is a function of productivity, which is a function of innovation. Productivity creates new products and lowers the cost of existing products. New products displace old products, shifting utility curves outwards, which creates wealth, given that income is the monetization of utility. Lowering cost curves frees up income to spend elsewhere, which creates wealth because it increases total utility, given that the individual can now obtain more goods. Real long-term per capita economic growth, which means an improvement in living standards, is always a function of productivity growth.