How about a satisfying ending?

I've recently read the third book of a highly-regarded apocalyptic story that left me thinking "is that it?"  The ending tailed away, as if the author didn't know what to do with his characters now they've  escaped from their life-long oppression.  And I've come to think that working and re-working the ending of a book is as vital to its success as a grabbing beginning.   Polishing those final lines, and tying off enough loose ends to allow the reader to make sense of our story, is every bit as important as the work we put into a story start.

In the apocalyptic trilogy, the main character says she's worked out what the baddie is doing to oppress her.  The trouble is, she never tells the reader.  And when she and her people escape from the artificially poisoned air they've been living in for generations, it's an anticlimax.  The narrative jump-cuts to her looking back at a dome of grey fog over the land.  This is the deadly atmosphere that's been oppressing her people for generations, but there's no sense of her having to struggle to escape from it.

What's missing is a Supreme Ordeal.  Surely people with the ability to make such an atmosphere, with the ability to monitor the lives of millions and terminate them at will, would have tech to prevent people from escaping?  But leaving doesn't seem to be a struggle.  There's no sense that the heroine has to breach any barrier, which I think would have to be there to keep such an atmosphere in. 

I think this should be the Supreme Ordeal.  Our heroine has overcome every challenge, only to be thwarted by an impenetrable barrier.  Which she then works out how to take down before her air supply runs out.  This would provide the tension missing from the book.  Instead the narrative jumps to a cosy scene of blue sky and green grass, with no struggle involved.  And the characters then just mill about aimlessly.  They don't seem to have any plans for the future.  They're supposed to be going to the sea, but it's not clear why.  They've found a cache of food, seeds, and tools, but there's no mention of people starting to grow food.

The end seems more like wish fulfilment that a satisfying story end.  I need some sense of what their plans for the future are.  And there are a lot of people still being oppressed back in the evil world they've escaped from.  What plans do they have to go back and rescue them?  There are too many questions left unanswered, and they're important questions that must be answered for a satisfying ending.  And that's absolutely vital if our readers are to leave our stories feeling satisfied.