If I want a Ferrari, I am forced to pay for it, fair or not. So instead I steal one while filing suit demanding that I should get one on my own terms.What other choice do they have? If you want to develop to iOS customers, you are forced into Apple's terms, fair or not. So now they are trying, legally, to get Apple to make changes. Change isn't easy, as we've found this year, but we shall see.
You seem to assume that Epic has some god-given right to sell to iOS customers on whatever terms it prefers. No such right exists.