One of the devices that Rudyard Kipling uses is symbolism. In this poem, he uses the symbols of East and West to talk about the population that lives in these areas of the world. Therefore, when he states that East and West will never meet, what he means is that Western and non-Western people will never be able to understand each other.
This could be seen as a way to justify colonialism. By claiming that the people are too different, those who are not interested in learning or trying to understand other cultures might stop caring or trying, and might see other people as inferior to them.