Looking at it from the angle that, youths who have not developed skills hugely depend in the economy to provide employment, which then amounts to economic instability, then you can agree that this could be a bomb waiting to explode, but when we have youth who have developed skill and making innovative moves, we can say that they are the engine of the economy.
The key here is the mentality to develope skills, curbing the need to be dependant on paid jobs, rather becoming employers to a large extent!
From my observation, demography only supporting factor on economic reality, what more important as economic indicator are economy structure, government institution, technology, capital, political stability and access to global market. So, youth statistics, quality, healthy and productivity can not figuring out future economic condition. Skilled youth without jobs create unemployment, abundant resources and capital without human resources bring limited growth and a good government without young demographic still able to make good progress or be developed country. Beside that not everyone can be an entrepreneur and a countries with many entrepreneurs are not always more developed. What i see in developed country, there are combination of professional workers, researcher, technician, productive employees, large companies with efficient bureaucracy and good governance, which mean healthy growth economy need ecosystem not everybody be a businessman.
Lets take example on some countries; High technology, high productivity, strong industry , big capital and institutional stability make Japan with small youth population and aging population can still be rich and advanced, Japan not doom. South Korea face low fertility and birth rate with aging population but their economy remains innovative because of their high quality human resources. We see demographic bonus failed without good institution in Nigeria, with its big youth population, rich oil resources but unemployment rate are high and inequality also wider. Population size only number not primary determinant can be clearly see in Singapore, small country, strong law enforcement, high capital from inward investment, good educational, without youth boom but very rich. So i conclude the formula of economic progress / development are demography , education, investment, industry, institution, stability, technology, and equal access.