China doesn’t have the same geographical advantages. China doesn’t have the opportunity to steal trillions in wealth from native lands and native peoples. China can’t make a new slave trade. China will be forced to compete with other powers, like the declining US and EU as well as regional rivals like India and Russia. China can’t recreate US global hegemony, and neither can any other country because all the low-hanging fruit has already been eaten
These geographical advantages aren't as important today as they were at the beginning of industrialization. As for the other things: They're all ethical issues and "international norms" established under US hegemony. The reason the slave trade isn't a thing anymore is because the US/UK-led global empire decided to collectively abolish it in the first place. The same goes for old-fashioned colonialist conquest & plundering, which the old European powers were forced to abandon under US pressure (among other factors).
All the things you're describing are features and consequences of the US global order, so why would anyone expect any of them to remain intact if that global order gives way to something else? The reason almost every single state, even totalitarian ones, adhere to "international norms" on slavery, colonialism, or nuclear weapon usage is because the consequences of breaking these norms would be highly disadvantageous, and would result in punitive action in the current global order. The reason why almost every single state - even the most totalitarian - holds elections (even if "fake" ones) and attempts a facsimile of democracy is because the current global order inherently lends democracies more legitimacy than autocracies.
Assuming the current global order disappears, why wouldn't totalitarianism, slavery, disenfranchisement of women, or even colonialist conquest make a comeback? There would be nothing to enforce the norms against these at that point – and any actor could easily break them with no consequence whatsoever.
Let us not forget that global warming is going to continue to destabilize the entire world with billions forced to migrate. Country after country will collapse into uninhabitable dead zones. China isn’t going to build an empire in the ashes left by this particular epoch, no one will and no one can.
External pressure is just as likely to incentivize empire building. Physical domination and control of habitable land at any cost will likely become very important, if not essential, and everyone will get away with it.
This is a new situation and I obviously could be wrong, but unless China figures out cold fusion or asteroid mining or something I don’t see them becoming the new global empire. We’re at the end of an era and something new is happening.
They don't need to figure out any of that. They simply need to be able to capture more energy than their adversaries, and that is possible without cold fusion or asteroid mining. The CCP only need maintain its current trajectory of development to be able to overtake the US by the end of the century. Unlike western liberal democracies, a high-tech totalitarian society like CCP-controlled China can expand and maintain stability even in a collapsing environment without being constrained by norms or concepts such as the rule of law.
Does the motive matter that much? It was the result of US/European abolitionist movements' success, who ended the practice within their respective empires, and which eventually extended into a global ban. The point is that the practice was banned & ended worldwide.
Reformist movements don't and can't exist under CCP rule period. An anti-exploitation movement in China would be crushed immediately, if it were even allowed to develop at all.