alt Hacker NewsMastercard and Visa also use immediate settlement models and basically always have done. The settlement buffer between end parties is created entirely by entities that are all basically banks.
There’s nothing special about Mastercard and Visa rails that prevents you recreating all the functionality that the broader ecosystem provides, without Visa and Mastercard. Hell all of that functionality could be provided by exactly the same companies and banks that provide it for Visa and Mastercard networks.
Because mastercard/visa don't personally bear any risk they are very happy to process refunds and chargebacks in the customer's favor. It's not a perfect system, but it's much better than direct bank debit where the customer has very little recourse. There is also a significant privacy issue. Today my bank can only see the sum total of my credit card purchases but not what I buy and from which vendor. Amex can see what I purchase but knows very little about me otherwise. I like this separation, and I like that it's hard for the government to get a complete picture of my financial affairs. I know credit cards get a lot of hate (here and elsewhere) but as a consumer I think they're exceptionally convenient.