Frankly, both payment infrastructures (Apple/Google) should be opened up. Heck, I wish there was a way to mandate building standard/open payment infrastructure for the web.
It's not there because platform vendors don't want it. We could have had it decades ago.
I'm not sure this is relevant. Having open infrastructure (whatever that means) doesn't mean that there'll be a seamless one-click purchase option for users; nor a zero-cost integration mechanism for developers.
Open infrastructure was too vague. An open payment standard, like OpenID/OAuth/FIDO.
There should be a standard, distributed payment system, it should be easy to switch providers, and it should be easy to make payments without going through all these proprietary systems.
It won't ever happen because there's nothing to gain for whoever builds it. And it needs to be build by the platform owners, precisely those that don't want it because they have their own payment systems (Apple, Google, Samsung, Microsoft, etc).
Understood. I wouldn't say that OpenID or OAuth are particularly standardised to the point where you can freely switch providers, though. That's where companies such as Auth0 are required, just as Stripe abstracts over different payments APIs.
It's not there because platform vendors don't want it. We could have had it decades ago.