I thought it was really good. Entertainingly done and plenty of thoughts about human nature to cog on.
I'm not entirely sure of the relevance of the hints at reincarnation and past lives. Maybe just a means to show that these aspects of nature reappear throughout history.
This Slate article mentions:
References Aleksandr Solzhenitsyn a bit.
There's also a definite climate change undertow. Old Seoul is under water - if levels keep rising, New Seoul will end up the same. I remember Meronym mentions something about despite their advanced civilisation, the Old'Uns' fatal flaw was of always wanting more. Greed again.
Slightly problematic representation of race in the film, with white actors portraying Asian characters - is it yellowface? The counterpoint being that all actors are made up to represent different races at different points in the film, and that it is meant to represent the interconnectedness of all peoples. That said - would have been better to have another Asian lead.