Not finishing is not letting go, most the time. If people are giving up because they don’t know what to do, it’s almost always in the middle: people tend to have start and finish be concrete and the how to transition is where they get lost: I’m very traditional in this aspect, as well.
But what I find in some movie writers have a great grasp of is leaving a sense of continuing on in their finality. Sometimes if you can show that there is a future to go towards, even if you don’t write that future, it keeps that sense of finality from inhibiting later chapters.
For example: ending of Angel was gearing up for an apocalyptic war that had maybe 10 people to shut close the gates of hell (or whatever the portal was). They know it’s their death. No questions about it. Yet they run in towards the battle for the continuation of this world.
And it just ends there. It allows a finality that there is nothing more to tell, and allows the hope of a future.
At the end of "Star Trek VI: The Undiscovered Country*, Captain Kirk quotes Peter Pan for their course settings at the e d of the movie: “Second star on the right and straight on 'til morning.”
This is an episodic series, and no matter how old the first crew got, people still saw them as continuing to explore the galaxy. Quoting Peter Pan gave notes of the agelessness of their work, and helps gloss over how many of the actors are now dead.
But it was a sense of finality be ause it was the last movie they planned on doing on their own. TNG took over and Generations wasn’t until '94, allowing the original cast to be mostly Cameos, except for Kirk.
This is why I have such a nostalgia for old school endings, where you give a short synopsis of their futures, but recall them to the current ending instead of giving an excerpt of an epilogue some few years in the future. Just a greater sense of continuation and finality, so that way I don’t feel like they are giving up.