I'm talking more about a slow decay that is not obvious to a single generation. One person in one lifetime wouldn't even smell it, but everything would be slowly corroding underneath.
Definitely not a big single disaster scenario. More like a "wait, we don't fix things anymore" or "wait, we have way less food variety than before" realization when it hits.
Nuclear war is overrated. Too focused to really damage distributed systems, too hard to start, too few working nukes. Many of the old rockets on all sides likely won't even fly correctly. Now drop world shipping via blockades and active war zones, and the industry collapse would be worse than anything Sarah Connor saw.