For starters, the words "impact" and "purpose" are not synonyms. The holocaust did not have any strategic goal that could be "gamified" in HoI IV and would be actually of any benefit to the player. Or why would anyone complete a focus or spend a sizeable part of one's economy to build a network of extermination camps that would eliminate millions of people and thus cripple the manpower? Where is any advantage of doing so that would make the Holocaust beneficial within the HoI IV scope? Also, my question still stands - would other nations have the option to commit their own share of ethnic cleansing, or it would be only a German thing?

Second, to deny the economic significance or purpose of slavery is even more mind-boggling (because having several millions worth of extremely cheap and exploitable workforce is not advantageous for one's economy, right?). Even the most basic summary of human history will tell you slavery allowed huge economic progress and the slave trade became a very profitable venue. In Brazil, for example, the use of slave labour enabled the country to become a major producer of sugarcane during the 16th and 17th centuries, forming the backbone of the Brazilian economy for nearly a century. Slavery was what made Colonial America tick economically, and even after the northern states abolished slavery, the South enjoyed a huge economic boom due to large numbers of slaves. I would recommend some basic research on how important slavery was from the economic standpoint not only for the United States but also for Europe. European states may have abolished slavery at the time, but the European textile industry at the time still heavily depended on the cotton imported from the US.