so the moral of the story is that life is meaningless?

[JolyJew СлаваУкраине]

basically, every single temple you explore is about finding meaning to life:
the shrine of ash is about pain and embracing it
the seat of infinity is about knowledge, even if it drives you mad
and the ice tomb is about just disconnecting entirely from the physical world

after you destroy all temples you fight the one that wanted to leave this world for a higher plane of existence. but as soon as you beat him and ascend this higher plane is just being stuck an infinite loop doing everything all over again

in the stories of the 4 shells most of them ended up dying because of their pursuit for meaning in life except mybe for solomon which read about his own future and accepted his fate.
all of fallgrim fell to ruin and disrepair because they all thristed for nectar which gave them spiritual enlightment and thus a feeling of a meaningful life

the only good ending in this game is accepting that life has no meaning and joining Baghead

that has to be one of the most depressing game conclusions i ever seen, i know soulslikes are supposed to be grim but this is just extreme...

[Lord Fane]

i wouldn't say its not any more depressing then lets say darksouls ending for example. You can choose to rekindle the flame, continuing the cycle. Or let the flame die. Bringing the world back to darkness ending the age of man.

I think mortal shells story is more about how the quest for immortality and power is a quest that only leads to corruption and more death. the abuse of nektar was the downfall. Consuming too much made it more of an addictive drug then anything else. tiel for example consumed way to much searching for his "spiritual high" that his skin started to boil. and the darkfather was so obsessed with becoming a god, he was punished imprisoned.

I wouldn't say the 4 shells had a meaningless life. from my understanding (I could be wrong) They followed hadern to fallgrim protect the seeds. but became too obsessed with consuming nektar. hadern realized then that all this crazy ♥♥♥♥ shouldnt have been messed with and wanted to take the rest of the seeds and leave. but Solomon believed that fallgrim could still be saved.

all that is a whole separate story. but as far as the ending goes. I think the true ending comes with the DLC. from my understanding the idea is to get your sister to ascend by gathering the remaining seeds. And fallgrim does get clean. (all-be-it still a very broken place.)