Thanks for your question. In many ways, you could say that “making the world a better place” was the explicit or implied aim of a large majority of philosophers throughout history; from Plato to Confucius to Marx to Singer. The big disagreements, of course, come from different ideas of what a “better world” would look like, and how we could get there.
For Plato, the better world is the one that is more in line with the “Ideal of Perfect Goodness”, and where people make rational decisions in accordance with timeless ideals. For Confucius, a better world is one where people act virtuously, according to the traditions of their ancestors. For Marx, the better world is the result of the revolution of the proletariat, while (Peter) Singer believes that we should act in ways that maximize the happiness of all life forms, including humans and animals alike.
From my point of view, the key problem we need to solve as human beings is the tension between living as fully realized individuals, and living in ways that will support best interests of humanity as a whole. If we can solve that problem, I believe we will also be able to resolve problems such as the self-destructive practice of war and the ongoing destruction of our natural environment, both of which are aggravated by our consumerist culture.