If Apple is not providing the app store infrastructure, why do they deserve a cut?
You bought your phone, it's yours. You're downloading an app from Epic's app store. Apple has no part in this transaction anymore.
It's the same as buying software for your computer. You buy a copy of, say, Turbo Tax, for your PC or Mac. You download it from Intuit's website, and install it. Why should Apple get a cut of that?
Apple came up with this insane concept that they need to be paid by developers to write code for some of their devices. It's a completely insane idea that took off because obviously companies want to make more money, but the reality is if you're not using Apple's infrastructure to distribute the software, Apple doesn't deserve a single penny.