You're quite right on your point about the distinction between imperialism and colonialism. I meant colonialism.
Something can exist alongside or in tandem with a system without being identical to or necessarily dependent on it. A great example is capitalism in China. Politically it is communist, yet it also has a huge capitalist economic sector. The capitalist economic system in China has raised hundreds of millions of people out of poverty, a feat no other economic system has even approached.
Japan is capitalist, is it also colonialist or based on racist exploitation? What about Sweden, or Germany, or South Korea? There are many capitalist countries that never had any significant empires or colonies, and certainly reaped extremely few economic benefits from them if any, that have done extremely well. What made them wealthy was industrialisation and capitalist economics.
Even the USA had barely any colonial presence, and any that it has had made almost no impact on it's economy which throughout it's history has been almost entirely driven by internal demand, and most of it's trade was with developed countries, not colonies. Yes it had mass slavery, but in fact ending slavery was hugely economically beneficial by allowing former slaves to emigrate north and take up jobs in the industrial belt.
Look, I'm not in any way denying that colonialist abuses were appalling, that we benefited from them, that there are lingering historical injustices that need to be faced up to. All of that is true. It's just got nothing to do with capitalist economics, which if anything actively contributed to the downfall of that system.