Interesting. I thought it offer fairly good Cash Back, no Fees, no hassle, ease of use. Even if it manage to reach 10% of the US iPhone users it will be a serious damage to other CC. While I may not get the best Rebate and Points when using Apple Card, I don't think those few percentage are worth it for my privacy.
Look at the personal finance scene in the UK—it's one of the more vibrant markets for banking right now with the likes of Monzo, Revolut, Monese, and countless others. Convenience and simplicity has prior art there.
It's also disappointing though, because it means Apple is not competing as a separate entity. What we want is for Apple to jump in be an actual credit card company. Then for all of them to try to destroy each other. (Unfortunately, now that I think about it, there are probably legal reasons that Apple is restricted in this regard. That's a shame. Basically means that it's Mastercard and Visa forever.)
The Apple card isn't competing with Mastercard and Visa -- in fact, it uses the Mastercard payment network. It's competing with credit cards issued by other banks on top of the MC and Visa payment networks (and AmEx/Discover, which unlike MC and Visa combine the payment network and card issuing).
I doubt the other banks are too afraid of Apple though, I didn't see anything so compelling about the Apple card that would cause it kill other credit cards. It's a slick product, but not game-changing the way that e.g. the iPhone was to entrenched phone makers.