If you young people who today belong to the first generation of the 21st century make an effort now, you may be able to create a happier, more peaceful world. But you can't take for granted that it will happen by itself, you'll need to take action.
Material objects give rise to physical happiness, while spiritual development gives rise to mental happiness. Since we experience both physical and mental happiness, we need both material and spiritual development. This is why, for our own good and that of society we need to balance material progress with inner development.