Wait wait, unironic take, I assumed that the entire concept of there being a war and a Demon Queen to defeat was a scam? The humans cut a deal with the last Demon Queen that we would send enough humans to Lucidia to keep all the monster girls fed if the monster girls stopped the wars. Then someone (probably Elly) created the anti-violence enchantment, and they started tricking humans to come to Lucidia. Why else Sofia be obeying all these crazy anti-sucubus laws? Why all the crazy temple nonsense?
If you told humans the truth, "Hey, we need lots of strong, competent men to go be cum-dispensers for Monster Girls," it wouldn't work. You'd only get perverts, and they would be too lazy to get the strength and competence required to actually satisfy higher-level monster girls. But if you lie to them and tell them they need heroes to defeat the Demon Queen, and that there will be glory and riches, then you'll get a better group of candidates. Note that the MC didn't even know about the enchantment until he got there, he thought he would be fighting violently (*I think?). AND THEN they send you off to earn 1 million eros, an absurd sum for most adventurers, which you could only get by feeding a huge number of monster girls, effectively ending a need for the war.
I think once we get to that part of the story, maybe there will still be a "Demon Queen" for him to defeat, but it'll seem really hollow. Somehow you'll figure all this out, and maybe 2-3 endings based on like, do you go back and fight Elena for lying to you, or fight the REAL Demon Queen or something.
OOO maybe get hired to be part of the conspiracy! You train lower-level monster girls to be good enough to handle the higher-level areas like the mountains.