What's amazing to me is how many people don't understand how Apple Card works. It is absolutely an Apple product through-and-through.
Goldman Sachs is only the issuing bank, the institution that provides the financial know-how to make the Apple Card work. If I have a Lotus Elise and drive it from one end of the country to another, did I buy a Toyota product because the Toyota engine is what powers the car and gets me from point A to point B? No, because Lotus developed and manufactured the chassis and what differentiates the car from any other is the user experience I have, which Lotus is directly responsible for.
Goldman Sachs is not the one that integrated Apple Card with the Wallet app and Apple Pay, it's not the one that is using Apple Maps to provide users with detailed transactional history without storing client information on their own servers. A co-branded card like you describe would be a Goldman Sachs Apple credit card that gives you 2-3% on Apple purchases through Apple and nothing else. People are focusing too much on the physical card and the lack of cash back benefits over existing credit cards. What they don't understand is that Apple Card is designed to incentivize the use of Apple Pay and give Apple a larger market share of the payment industry.
Apple created a new industry with the iPad and the Apple Watch, and they're going to do it again with the Apple Card. You can say that tablet computers existed before the iPad, and smartwatches existed before the Apple Watch, but that argument fails to take into account the "how" of Apple's execution. Before the iPad, tablet computers tried to run x86-based Windows, so they had to be large and heavy to accommodate the processing power and display size required by the operating system. Apple realized that people didn't want to carry around such devices, and yet they also wanted a device that could meet their productivity needs so that the price of such a device would be justified. Hence, the iPad was light, but it had an operating system that was built from the ground up to be used with finger input, rather than a keyboard or stylus, yet had the flexibility of using an app store where independent developers and large software companies alike could distribute their software. Likewise, when the Apple Watch came out, people compared it unfavorably to wristwatches. What they failed to understand was that while the Apple Watch resides on your wrist and happens to tell the time, the similarities to any existing watch end there. Apple has created a whole new industry based on having your information available at a glance and pushed the health and fitness capabilities of smartwatches.
These devices continue to be market leaders in their respective segments, and both were ridiculed by the masses when they first came out. Apple Card is just Apple being ahead of the curve again.