First issue, the biggest issue with the slave trade is that it isn't intrinsically connected to Capitalism. Its simple statistics, correlation =/= causation. The Slave trade existed way before capitalism's inception which was around 1600s. People formed empires and people that lost in wars would become slaves. During that time we went through a variety of economic systems like feudalism, monarchism, etc. So you can't pin slavery simply from capitalism. It makes absolutely no sense and its what NYT 1619 tried really hard to do.
Second issue, you are confusing colonialism with capitalism. While I agree elements of capitalism reinforced what happened in colonionalism a lot of actual capitalists were quite progressive on these issues. Simply put, decreasing the purchasing power of countries and holding them back would be good short term for economy but not long term. If they had more purchasing power they can put money back into economy (and it'll give them money back) and that will just make economy bigger.
Third issue, my take is a lot of issue with capitalism is that we aren't competing fairly. I think my positions are encapsulated in idea of capitalism for all. Let everyone be able to compete fairly and stop barring them from bullshit policies like redlining, systemic racism etc.
The fourth issue, I think strong labor can co-exist with capitalism and it isn't really a dichotomy. For your apple issue, the reason China is able to sustain its economy is with state control and a lot of human capital. In fact, a lot of issue with China is their extreme state control that is a symptom from communism they had with Mao.
When I focus on the deaths of communism, if we talk about Khmer Rouge you got people that were essentially purity tested, and then you were killed if you disagreed. It was ethnic cleansing. During Gulags, you got bourgeoise people sent to gulags. I mean look at the great leap forward. You had what like 35 million forecasted killed? I mean look at Pol Pot and shit man. That shit was heinous. All these issues have to do with top-down state control obsessed with eliminating class.
But, now that I've written all this out I think I know what you are saying. Communism and Capitalism are really big labels. So its hard to peg them one way or another. But my issue with that is with all the times Communism has been tried why does it always seem to turn the country into an authoritarian shithole? Is it with how Russia got rid of anyone that wasn't a Marxist-Leninist and only Marxism-Leninism has been tried (and been an abject failure)?