I think the fact that deltarune feels like the “dark timeline” for all the original characters is a sad kind of hubris… everyone’s goal in undertale was to get back to the surface world and live happily in the sunlight, but the struggle of living in the underground and striving for more together was what brought the main cast together in the first place. it’s why alphys built mettaton, it’s where papyrus found his sense of purpose, it’s how undyne was able to make friends. all of them wanted so badly to live “better lives” on the surface, and deltarune shows what that “better life” would have looked like… and it wouldn’t have been better. because maybe the monsters wouldn’t have been trapped, they wouldn’t have had to train and fight and suffer, but they also wouldn’t have had each other.