I don't thing it is healthy to have big entities like this control fundamental services like payment processing. How long before the opaque governance of the App Store is applied to their payments offering? How long before activists start making this a new vector for deplatforming? Apple also announced a news offering ( https://www.techradar.com/news/apple-news-plus ) and I think the same concerns apply there.
You're misunderstanding how card networks work a little bit here. This is a credit card, not a payment processing service. Two different sides of the network. "Deplatforming" refers to getting kicked off a given payment processor, which is an entity that gives a merchant access to a card network (in this case Mastercard).
Perhaps issuers like Goldman Sachs could start banning their customers from using their card at certain merchants. But this wouldn't come from Apple -- they've already said they've engineered themselves out of that kind of control.