This is probably why they always make statement that this is "demon world", hence why it's better not to put human mindset on it. Kind of why we don't question awful rule in the past since we couldn't apply it nowadays and it's just different period.
I guess the reason why Iruma never thinks it that much is because so far he's been in "survival mode" in human world. Dude didn't even go to school and worked his best just to live.
Where's the child protection service because I'm pretty sure there's law regarding child labor too. Gosh, Iruma's parents are messed up.
Look man I don't feel like writing a essay on this lol so I'll try to keep it short.
1- all social constructs in fiction reflect a human point of view. Its just like that. Anyone who says otherwise is deluded or is an alien. Demon society in this manga is constructed using a human idea of meritocracy, of hierarchy, of society. If this was supposed to be soooo alien and different, why do they wear clothes? Why school, borders, parties, aqua parks, amusement parks? Why is work and friendship a thing? All human concepts. Demon world is awfully close to human world in many things, so makes sense to compare them.
2- Iruma isn't presented as a feral child. He knows what school is, he speaks a language, he has proper understanding of emotions and social queues, he isn't riddled with crippling trauma and anxiety (except 2 chapters where he is drugged and comes out almost unharmed from confronting his past) Seems like all those years in the wild only left him with the good consequences and none of the bad. Early on, the school he goes to introduces the rank system and implies that the lower ranks are just plain worse than the better ranked ones. They have less benefits, they are denied some food, which is available only to upper ranked demons. Theres a big ass classroom with insanely cool shit only 1 class with exceptional demons in it can use. Sorry, the demons with high ranking can use. No one says anything about this. Iruma knows how to read and write, he has been exposed to SOME human knowledge. He is presented as a morally perfect character. Doesn't. Bat. An. Eye. At this insanely elitist attitude from the school. We still don't know if the rank system applies to all of demon world like the ranking system in china, but if bablys is any indication, the world is fucking insanely unfair to the big majority of its inhabitants.
3- now my worries about this is that so far we've been presented with morally gray characters some times, but there's always a clear idea of who's good and bad. Good demons respect hierarchy and titles, bad demons don't. Good demons play the social game, while the bad demons denounce it. I fear this author truly holds meritocracy and the natural rule of the strong as values somehow. Nothing so far has shown me that there's some nuance in the world view. I hope I'm wrong about this and it is the case that the moral nuance will come up later as Iruma matures, and this is planed out to be a long 1st act of a very long story. Maybe it is so. If not then I won't drop the manga or nothin, I'm not that politically committed, but I'll feel very disappointed