Every time, when I want to make a second playthrough of this mod, I remember endings and how devs acted annoyed about people asking about ending and proudy/edgy (can't quite describe feeling) about their unwillingness to make at least bitter sweet ending, not only doom and gloom. Perhaps something is wrong with me, but I understand appeal of making a game with only bad endings, like there isn't enough sadness and grief in our real life.
Want that sweet feeling of imminent doom coming on your ass?
Think about billions of IRL asteroids that can't be shot down or even detected by modern equipment before hitting the Earth. Or even better - a singularity or neutron star approaching our system and humanity can only host a handful people on shitty space station (with almost non existent protection from space radiation), let alone building a functional Ark ship to save anyone.
Want something more grounded?
Dictators with nukes can suffice your desire for negative emotions in life in no time.
Honestly, my investment in plot was crumbled after I realized that "one essential npc who catched my arrow by accident week prior" turned out to be the bastard who would ruin everything in scripted cutscene. After this shit happened - I stopped to take this mod seriously and care about characters at all. If I wanted to find myself in situation that none of my actions can change a general outcome in story/world - I wouldn't play an RPG. Some time after I played Nehrim and cannot look at Enderal as result of devs thinking: "we have mod series with developed setting and mechanics, but we are have a desire to make our own game on normal engine and we cannot design world that reached age of industrial revolution as side project, so fuck it - let's end series at any cost". Lack of side quests also support this theory, I think.
All my theory crafting aside, linearity seriously hurts of replayability of the mod even though I liked some of mechanics.