They can start by improving the livelihoods of their members, by helping then to save money for the future. Or credit unions can assist their members borrow funds to start small income generating projects that help raise their standard of living.
Once this happens successfully, the family of members benefit, in turn their communities benefit and the country benefits or the world at large benefits. So yes, credit unions can help build a better world. In advanced countries, large credit unions have become fully fledged commercial banks providing financial services to more people and businesses in those countries.