Would it be boring/unrealistic/silly/cliché if most characters only had this main motivation for most of a story: saving humanity/their country/their familly/themselves.
The setting is medieval fantasy, a war starts with an immortal being that cannot be reasoned with. It is like a genocide that only ends when the last human is dead, and the characters are aware of it. They know that in a few days, weeks or months at most they will all be dead. There is no way to survive this. How would people react after their world collapsed suddenly, facing certain death in a near future?
In my story some characters just give up and let themselves die. Some hide in small groups. And the main majority of the humans decide to stick together and fight, even though this is futile and that they are doomed. My main heroes are part of the group of characters which decided to hold on as long as possible. My problem is that I feel that they lack defining traits because they all have the same goal and the same motivation: they want to survive, they want to save the world. Money, power, revenge... none of those things matter anymore. It is all about surviving.
I have a pretty precise outline of the events from the beginning to the end of the story, and the actions of my heroes always seem logical, but what I feel I miss is character arcs/motivations. The differences between characters have been diminished because they are in a perpetual life-or-death situation. What they cared about before does not matter much anymore to them. They lack secondary motivations apart from saving themselves/the human world.
Would such a lack of secondary motivations be a problem and if yes, how to fix it?