China wants Africa for primarily its natural resources. There's nothing wrong with that, as China wants natural resources, and Africa's willing to sell them. The "conflict" lies in how China prefers to deal with African nations. China deals directly, and only, with the government in power, and avoids grassroots actors and the local community. Thus, to China, the government represents the country. To many in the West, because the governments are seen as illegitimate, China's dealing with the wrong entities for the countries' resources; China should instead work with the grassroots actors and local communities. China doesn't do that because
A) The ultimate authority of the country lies in the government, not the people
B) It's extremely messy to deal with that many actors when you can deal directly with the government
That's where the conflict of ideas lie.
Common criticisms include that China undermines the West's way of dealing with African governments, which usually takes the format of "Liberalize your economy and democratize or you won't get investment", while China goes "This is a market relationship. You give me this, and I'll give you that", which is basically non-interference. The government of China and the African country likes this as it's quite clear and requires no adjustment. Western NGOs dislike it because China doesn't include preconditions, which China doesn't actually care for. China's mentality is, "That's your country. You take care of it your own way or not at all".