Here is a question I have not seen a satisfactory answer for. Why is having an App on iOS a must have? It seems like any discussion about the market fairness of Apples policies requires a shared understanding of how necessary the ecosystem actually is. If you can freely choose not to deploy to that ecosystem then you can vote with your "wallet" so to speak. If you can't freely choose however then there is an argument…
At any rate, just because a platform is popular and will make you more money doesn't mean you have a legal right to force that platform owner to do business with you.
(Unless it is ruled as an "essential facility", which is what Epic claims, but I think is a huge stretch and not likely to be accepted by the court.)