The correct answer to this open question is the following.
I think Kipling’s attitude toward imperialism was of supporting the idea that white people were superior to blacks and indigenous people.
Indeed, his poem dramatically expresses some issues and difficulties of imperialism. We could say the poem includes a justification for colonization. Kipling stated that colonizing foreign regions was necessary to develop and modernize the world. That is why he called the white man’s burden to lead this task.
English author Rudyard Kipling wrote the poem in 1899, in the times when the United States had won the Spanish-American War, and as a result of this, the US took possession of Guam, Puerto Rico, and the Philippines, which were part of the Spanish monarchy.
At that time, Europeans sadly believed that they were a more evolved race who deserved to take over others. This is related to the term "Social Darwinism," which is considered to be imperialistic and racist.