That's only true of some methods like using exploits and other vulnerabilities, or mass-surveillance style methods. It's not true of other types like confidence tricks and social engineering, eavesdropping and potentially watching passwords being entered or getting them on camera, phishing, fake wifi points, tailored viruses, or cookie hacking. Those methods can be designed for a specific target. Of course, there's also the good old-fashioned method of getting a warrant for data.
The entire concept that the government has "a right" to this data - an argument I've seen judges actually make to justify these activities - is ludicrous. They don't have a right to it by default. They have a compelling interest in the data/information if and only if there is enough reason to believe someone is up to criminal activity. In which case they should have no problem at all getting a warrant.
Which enemy?
Regional rivals: North Korea and Iran
Authoritarian partners/allies: Turkey, Saudi Arabia, a bunch of other Middle Eastern countries
A bunch of countries flirting with authoritarianism: Brazil, Hungary, Poland, Israel
If that sounds dumb to you, you should rethink the statement about Poland and Hungary.
Apple devices are sold all over the world, so there's no way of gaining access to the enemy's devices without that method also being applicable to everyone else. Actually using them on everyone else is a different matter.