A US bomb from World War II explodes at a Japanese airport, causing a large crater in a taxiway

Nope, they just become less predictable. Which is why in some parts of Germany you can't build as much as a garden shed without having EOD check the land first. In the more heavily-bombed areas it's not unusual to hear on the radio that you're to avoid downtown today between 10 and 12 because they're disarming a 500-pound bomb they found during roadwork.

And yes, the fact that an unstable bomb capable of trashing a city block is mundane nicely illustrates war's potential to fuck things up for generations.

Japan might want to get that land under and around the airport checked. There might be some other surprises hidden down there.

Worse, the chemicals inside deteriorate to somewhere between "this detonator is completely trash" and "surprise fireworks".

They don't make 'em like they used to

I'd guess that's probably true for most of them, this one is probably an outlier