Okay, so I feel like the manga flew threw all of this WAY too fast, but this is actually a pretty interesting concept. It shows the failures of the reincarnation/afterlife system in correcting behavior. At a certain point if you’ve done something so bad you get turned into a demon there’s nothing to look forward to in life at all and all you feel is pain (but because you’re not human you have to become strong to survive amongst monsters). That just creates a downward spiral and the person never wants to be good in their current life (when its only pain) to get a better next life (so literally the opposite of what the system’s trying to do). This is a pretty interesting point and actually true for a lot. Blanket punishments will always miss a number of individuals, but they’re just forgotten as we generally only care if it works for most.
The other thing touched upon is that the MC is basically a god himself and can do pretty much anything; even directly undermining the system created by the gods when he decides it isn’t being helpful. This is stupid power and arguably too great of a reward even if the mc was crazy generous and kind in his past lives. I mean is the MC wanted to, he could do literally ANYTHING. That’s insane. If his personality was different no one could stop him.
Also this was a very interesting take on demons. They aren’t some other species, but just humans that have lived poorly in their past lives and now have to suffer a life of only pain because of it. Again the chapter went through all of this too fact, but definitely some interesting concepts and world building ideas. Now if the quality of story telling could just match the story (though I guess this series isn’t going for “good” writing considering this and previous chapters and the premise)