Yeah, but what if your 150mm ammo requisition is intercepted .....It could happen.
It could. The enemy could also in theory invent a superior air defense missile and a giant phased array to go along with it. So disband the airforce because it could happen?
Sabotage and disinformation have pretty much always been a part of war. A german unit managed to disguise as americans during the ardennes offensive and sent an american unit packing because they were supposedly about to be replaced at the front.
Nothing fundamentally changed when C3ISR became C4ISR. Computer networks added new ways to disrupt things but that simply constitutes an expansion of the tools of the trade. Cyber Warfare does not replace anything, it merely adds new options. I don't see how the presence of it would make artillery obsolete.
Russia has already tested decoupling its part of the internet from abroad. If you strike first, start by decoupling your network from the rest of the world.
To turn your argument around: What if your hacker farm becomes useless by a 20 Dollar grenade blowing up its electricity supply? Easy to repair. Lets up the game: What if a submarine (Losharik comes to mind) places shaped charges over all subsea cables connecting your nation with the rest of the world and someone triggers them? Let us leave the realm of mere theory: It has placed them, that is the reason for its existence.
I think that this whole idea of network centric warfare is somewhat naive. Look at what happened in Ukraine: Jamming. Forget about wireless networks in a peer war. Satellites will be shot down, the electromagnetic spectrum will bristle with noise. Is hacking a part of warfare now? Yes Does it make anything obsolete? No
Critical infrastructure should not have an IP address. I think that the most useful aspect of IT based attacks is to be found in measures short of war. Sabotaging the economy of the enemy while maintaining plausible deniability is a bigger threat than interference with the military supply chain. Of course there were successful malware attacks on military infrastructure like the Israeli Stuxnet sabotage of Irans centrifuges. They usually require spies at the place (no network connection) and in-detail knowledge of the facility.
In contrast something like a steel plant with its Windows CE based security hole of an operating system is a trivial target. The whole IoT pandemic of microcontroller infested networked devices makes everything from church bells to IP Cameras to milling machines available on the net. Often without the need to exploit security loopholes: The interfaces are HTML and show up by simply typing in the IP. No password required. Add naive employees susceptible to opening attachements to the mix and it becomes pretty simple for a state actor to take down most of an economy.
The military is not immune to cyber attacks, otherwise TSMC would not build a separate US Factory for backdoor free military chips, but it is much less vulnerable than industry. Pick the low hanging fruit, sabotage the enemies economy and don't even declare war in the first place. Economic coercion and bullying work most of the time