Much of what you wrote is debatable... not by me... but historians... here is a summary of that debate taken from Microsoft's AI engine.

The Atlantic slave trade had a complex and varied impact on the development of African empires. Some historians argue that the slave trade contributed to the emergence and expansion of powerful states such as the Asante, Dahomey, and Kongo, which were able to profit from selling captives or exchanging them for European goods such as firearms, textiles, and alcohol12 These states also used their military and diplomatic skills to resist or manipulate the European traders and maintain some degree of autonomy3

However, other historians contend that the slave trade had a largely negative and disruptive effect on African societies, as it increased warfare, violence, and instability, and drained the continent of millions of people, especially young and able men45 The slave trade also made African economies dependent on European trade and linked them to the world market in an unequal and exploitative way35 Many regions of Africa suffered from depopulation, underdevelopment, and social fragmentation as a result of the slave trade45

Regarding depopulation and high birth rates, how much was due to slavery and how much was due to historical tribal warfare is also debatable.

Most Islamic nations in North Africa and Middle East have long histories of tribal warfare and slavery. Some argue that slavery was used to subsidize the labor force and polygamy emerged due to all the males that died in warfare. So, high birth rates, polygamy, and slavery all seem to stem from constant warfare and would have existed with or without the Atlantic slave trade.

How much the Atlantic slave trade contributed to an increase in slavery vs how much it simply diverted slaves to the European colonies that would have gone to the Middle East or elsewhere is unclear. What is clear, is even as the European countries and the US tried to end the slavery it continued unabated even to this day to some extent.

It was western ideology that changed the view of slavery from an accepted institution to an intolerable one. So, it is hard to say how much slavery would exist today without western influence. What we do know is that there are more slaves today in the world than at any other time in history.