What are some happy endings that really wasn't all that happy?
Mad Max Fury Road. They defeat the tyrant, and get the control of the water valves. Then they open the valves and seemingly keep them open. One problem, how long is the water reservoir gonna last now?
Logan's Run. The city dwellers are freed from the computer's iron-fisted rule, and Carrousel. But their city is in ruins, and thinks to the computer providing everything. They don't know how to live without it. The city dwellers are going to start dying off real fast.
Depends on the apocalypse. If it’s sufficient to wipe out global trade and logistics chances are they’ll be rebuilding in the Stone Age, especially if there are no skilled craftsmen like smiths to keep even the most basic tooling working. Modern civilization has huge requirements for a stable supply of power and highly specialized professionals to keep it running. Get a Big apocalypse and you’ll lose enough of those people to make it impossible to re-start civilization.
That's exactly my point, the comment I'm responding to said that all apocalypses were unrecoverable.
We built up our current civilization starting in the stone age, so being knocked back that far isn't inherently unrecoverable. We can do it again. (And no, there isn't an absolute dependency on fossil fuels that are now gone. There are other ways to industrialize than just the exact specific route we took the first time around. Just getting ahead of that since it's a very common counterargument about such things).