A people can mature in long, developing ways that individuals cannot. As a people matures over centuries, individuals and groups within that people will be tempted to discard the slowly-developed elements within the people's culture, the elements that actually make the people mature.
Individuals are only as mature and developed as the people group if they cling to the long-developed principles. Every individual, and even the group as a whole, can abandon the people's maturity at any time. We do not automatically, unstoppably retain the maturity of our people just because we enter the world at a later point in time than others who carry forward the people's patterns and principles of maturity. We can always lose the maturity of our people if we reject the principles that brought the maturity.