Another trope I want to challenge is the idea of a single apocalyptic event changing everything. The closest we've ever been to a real apocalypse is the Black Death and that wasn't a single instantaneous event - it was a gradual apocalypse reaching different regions at different times. There was also a lot of ambiguity as people didn't have the right information to understand what was going or react accordingly.
Honestly, the Black Plague was only an apocalypse in term of a body count and area. There were even multiple outbreaks over a period of time. It definitely changed people's world view, but not in the way most people probably think of today, or appears in a lot of post-apoc fiction. It was the dark ages, for most people life was shitty before, shittier during and slightly less shitty again after.
You want something that has correlations to most apocalyptic fiction, try the fall of the Roman Empire. That was a paradigm-shifter for most of Europe, and not all of a sudden. But it would have seemed similar to a lot of post-apoc fiction we have today. Also, it was a gradual chain of events, like you said.