I think the bottom line is this. Apple is making a massive profit for doing minimal work here. It's estimated they profited $360,000,000 so far and their only contribution was to allow the app to be download.
Given that we don’t live in a communist county, making massive profit for minimal work, even if true, is not against the law.
Putting that aside, if you think that was Apple’s only contribution, I suppose your understanding is that Epic didn’t use any of Apple’s intellectual property, it’s SDK’s, it’s code, it’s development tools, etc., nor is Epic benefiting from the audience that Apple has created for them through Apple’s own hard work.