I disagree with your premise that by Apple putting the subscriptions where they did was to make it difficult to cancel. I also believe there are many questions asked of the entire Apple infrastructure on google everyday, because it's people don't read the manual.I guarantee you if I asked my mom — and I’d consider her pretty close to the median in tech literacy — right now how to cancel a subscription that’s billed through the App Store, she wouldn’t know. If I asked her to find it, she probably wouldn’t be able to for quite some time because the way to get there doesn’t actually make sense. She would Google it.
Again, “all your subscriptions in one place” wouldn’t have to go away. This would enable developers to allow cancelling subscriptions directly within an app, which again is where most users would likely expect such functionality to be available. You look for a redo button next to the undo button. You look for a paste button next to the copy button. You look for an unsubscribe button next to where you tapped the subscribe button. This is UI/UX common sense, if you can learn how to look past your own nose.
It’s long, long been a practice for companies providing a subscription service to make it difficult, obscure, or annoying to cancel a subscription, which is probably part of why AOL still had over two million dial-up subscribers in 2015. Apple primarily chooses “obscure,” but it’s no less sleazy (especially given recent rampant App Store scam subscription apps). Making it difficult/obscure/annoying to cancel is not how I’d like to operate — it gives me more incentive to make users want to stay, rather than forget to cancel — but Apple currently gives me no choice.
I googled "how to cancel an apple subscription", there is nothing hidden about the way Apple implemented this and I'm sure its documented in the ios 14 release guide.