The main problem with a lot of these stories is that there are combinations of iPhone models, operating systems, and settings which are believed not to be breakable by general law enforcement agencies, and others which are known or strongly suspected to be.
Apple tends to make its claims regarding latest iPhone model combined with latest iOS version combined with particular settings.
Thus, for example, in the San Bernardino case, the fact that the phone in question was a 5C mattered. The 5C is not just an older phone, it has different security-oriented hardware inside, and that does change the security characteristics of the device.
Also, the Apple statement you keep pointing to said that Apple, as of iOS 8, is unable to retrieve or reconstruct the key used to encrypt the phone's storage. Which is true -- Apple cannot do that, and has designed things so that Apple cannot do that. What the FBI wanted in that case was not for Apple to supply a key or a passcode (which they don't have). What the FBI wanted was for Apple to create and sign and load a custom firmware which would disable anti-brute-force protection for the passcode, allowing the FBI to determine the passcode via brute force. Apple could do that, but refused to do so.
And for completeness' sake, that avenue is no longer available on more recent phones with more recent versions of iOS; performing an iOS update now requires the passcode, regardless of whether the update is initiated from the phone or from a connected device (even one previously designated as trusted).
There's a difference between a backdoor and a vulnerability - as exploited by a third party, say, Cellebrite. Nobody claims that any OS is free of vulnerabilities.
Apple tends to make its claims regarding latest iPhone model combined with latest iOS version combined with particular settings.
Thus, for example, in the San Bernardino case, the fact that the phone in question was a 5C mattered. The 5C is not just an older phone, it has different security-oriented hardware inside, and that does change the security characteristics of the device.
Also, the Apple statement you keep pointing to said that Apple, as of iOS 8, is unable to retrieve or reconstruct the key used to encrypt the phone's storage. Which is true -- Apple cannot do that, and has designed things so that Apple cannot do that. What the FBI wanted in that case was not for Apple to supply a key or a passcode (which they don't have). What the FBI wanted was for Apple to create and sign and load a custom firmware which would disable anti-brute-force protection for the passcode, allowing the FBI to determine the passcode via brute force. Apple could do that, but refused to do so.
And for completeness' sake, that avenue is no longer available on more recent phones with more recent versions of iOS; performing an iOS update now requires the passcode, regardless of whether the update is initiated from the phone or from a connected device (even one previously designated as trusted).