The argument that this would be some kind of cryptographic back door seems a little specious to me, and I'm usually the biggest edgelord imaginable when it comes to decrying government surveillance.
If we were talking about a safe somewhere, and the government asked the safe manufacturer to create a physical device that makes it easier to open existing safes, that would not seem reasonable to me, but it also would be ludicrous to claim that represents a "back door." If that's a back door, then the back door already existed.
So in Apple's case, the government says "we need the data out of this device" and that's apparently a solvable problem. Can someone please remind me why it's so cut and dry for Apple to just say "no" and that's supposed to be OK?