There aren't a lot of alternatives in the smartphone space. If you don't like Android, you're stuck with Apple. Now if both are abusing their power, using your reasoning, you're supposed to say and do nothing ?
Or what goes into each game console, my cable provider installs on their set top box, and so on.
One could, you know, make a case that it should be illegal, go to court to get that official, and then the way to implement your own payment processing is open.
But beginning at the last step, is totally the wrong order to do these kind of things.
Besides that, Epic and Apple had an agreement the moment Epic published fortnite in the app store. If they dont like the contract, they can leave. Again, if they think the terms are illegal, go fight that out BEFORE you implement something that breaks the contract.