What is Chinua Achebe's core critique of Joseph Conrad's Heart of Darkness? In what ways does Things Fall Apart offer a response to the dominant image of western imagination?

Chinua Achebe's novel Things Fall Apart addresses colonization and its negative effects on the indigenous people who are colonized. In Things Fall Apart, Achebe tells the story of a Nigerian village that is wracked with problems when European settlers impose western customs on the local people.Like Joseph Conrad's Heart of Darkness, Achebe's novel is interwoven with themes of imperialism, race, and human nature. Unlike Conrad, Achebe tells the tale of European colonization from the perspective of the culture being colonized. Achebe addresses themes such as the violence of imperialism and the devaluation of indigenous cultures by white-dominant colonists. Heart of Darkness presents the destructive effects of colonization on the colonizers. Things Fall Apart tells the opposite story: one in which colonized cultures suffer as a result of imperialism. Achebe's novel is powerful in its telling of the other side of the story. In this way, Things Fall Apart is a rebuttal to Conrad's Euro-centric version of the story of imperialism and the dominant image of western imagination.In Things Fall Apart, Achebe develops themes related to colonization through the characters in the novel, and much of his criticism of the ideas in Heart of Darkness is evident. Achebe made his opinion even clearer in 1975 when he delivered a lecture entitled "An Image of Africa: Racism in Conrad's Heart of Darkness." The lecture (later published) sparked much debate regarding Conrad's beloved work. In this lecture, Achebe flatly describes many of the things he finds problematic about Heart of Darkness. Achebe's central argument is one against the dehumanization and racism with which Heart of Darkness is fraught.
Can nobody see the preposterous and perverse arrogance in thus reducing Africa to the role of props for the break-up of one petty European mind? But that is not even the point. The real question is the dehumanization of Africa and Africans which this age-long attitude has fostered and continues to foster in the world (Achebe, An Image of Africa).
In both Things Fall Apart and later in An Image of Africa, Achebe's core criticism of Heart of Darkness is that it dehumanizes indigenous people and glorifies colonization. In Heart of Darkness, Conrad calls Africa "the other world." Conrad describes African people as "savages" and distances them from the white visitors, writing that
They howled and leaped and spun and made horrid faces, but what thrilled you, was just the thought of their humanity -- like yours -- the thought of your remote kinship with this wild and passionate uproar. Ugly. Yes, it was ugly enough, but if you were man enough you would admit to yourself that there was in you just the faintest trace of a response to the terrible frankness of that noise, a dim suspicion of there being a meaning in it which you -- you so remote from the night of first ages -- could comprehend (Conrad, Heart of Darkness).
In fact, one of the central themes of Conrad's work revolves around the idea that Marlow and other European travelers might at their core be related to these so-called savages. To equate evilness to blackness is a highly problematic theme, and one for which Achebe derides Conrad. Achebe turns an examining eye to the racist ideology behind these passages and argues that Conrad's depiction of black people both dehumanizes and distances one human group from another.