There are techniques of Buddhism, such as meditation, that anyone can adopt. And, of course, there are Christian monks and nuns who already use Buddhist methods in order to develop their devotion, compassion, and ability to forgive.
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.