If a smooth cancelation is so important to users that it justifies a 30% upcharge, other payment processors will compete. They can even advertise the easy cancelation during checkout next to the payment method (“install the stripe subscriptions app or go to stripe.com for one-click, prorated cancellations!”). I think once one of them does it, they all will. If the injunction goes into effect in 90 days, it will be a gold rush for everyone who gets to finally compete with Apple Pay. This will induce a bunch of rapid innovation in the iOS payment space.
The thing that I think you're perhaps missing is that Stripe etc. will be competing with Apple for developers. Letting developers make it harder for consumers to cancel something is a feature, not a bug.
Stripe etc. do not care about competing for consumer favor. Apple does. As far as any large company is on the consumer's side, Apple is, because they need me to buy another iPhone more than they need me to buy a subscription to somebody else's app, even at a 30% vig.
This is a deeply threaded discussion, but if you look up there, you’ll find that people are arguing that users will choose Apple Pay over other payment processors or refuse to use apps that don’t offer Apple Pay. That’s the context in which my comment is written. If it’s true, then app developers and payment processors will need to respond to that market demand. If users don’t care, then of course developers and payment processors don’t need to care either (absent regulation).
It’s very wholesome (or, naive) of you to think that developers will give users the choice for a less predatory payment gateway out of the goodness of their hearts, but that’s not going to happen.
Making it harder for users to cancel their recurring payment is a feature, it’s customer retention, the only choice you’ll have is whether a given site or payment processor is so egregious that you will forego use of the service entirely rather than take the risk.
If not being robbed is so important that it justifies buying locks we might actually decide that robbing should be illegal and punishable by jailtime....