Actually, one of those two isn't necessary – the payment network.
It's possible to build a payment platform _just_ on top of banks. We're doing exactly this at Sway.
In Europe this is driven by Open Banking initiatives. In the US, this will land next year with the FedNow service.
In other parts of the world, like China, Brazil, and India, instant (and free) payment networks have existed for a long while.
https://sway.money
https://standards.openbanking.org.uk/customer-experience-gui...
https://www.frbservices.org/financial-services/fednow/about....