But let's for a moment assume that Apple does not intend to shut down the App Store. There's something they can do that would have both good optics and be actually productive.
Strike the mentions of In-App Purchase from section 3.1, and replace it with a set of hard rules for qualifying services. The services must be as easy to unsubscribe from as they are to subscribe to, may not use misleading "dark patterns" to trick people into staying on longer than they intended to, and must be straightforward to understand. In other words, the kind of rules that would usually come from hard laws or region-level consumer protection practices.
Sprinkle on some APIs implemented by the apps to make it possible to get to the appropriate aspects of the other payment solutions from within Settings, or the App Store subscription panels, and there's suddenly a whole lot more freedom without the risk of a precipitous drop of usability or confidence. The people that have been kicking up a stink about this for ages have been doing so because they've been trying to run businesses in a hostile environment – it's in their interest to handle this well.
I mention optics because Apple could still reasonably come out of this as a pragmatic, customer-focused leader. Not a terribly responsive one, mind you, but a leader none-the-less.