I'm honestly terrified that America's nuclear missile silos are going to get "upgraded". Let them keep their 8 inch floppies and text interfaces, for the love of god. It works fine the way it is.
Only 70? That's a stretch. This is 2019, after all, not 2015. Those 70 dependencies are only the first-line dependencies. Their dependencies will bring in another thousand.
Hardware fails over time and gets increasingly less reliable and harder to source. These types of upgrades are mostly about maintaining existing functionality on modern hardware.
In the case of nuclear missiles, this is entirely a good thing. If both sides can just maintain Potemkin nuclear arsenals we'll achieve gradual disarmament through obsolescence.
We might hope that at some point in the early 2100s, somebody will notice that none of the nuclear missiles work anymore, and with any luck, the engineering knowledge to create new ones will have been lost.