For the DVD thing, I think you're confusing player PoV elements with Roy's PoV elements. We, the players, know that something lewd will happen to the girl(s) when they're left to their own devices under certain circumstances. We, the players, know that to stop that, we need to either have Roy take the girl(s) on a date, or otherwise give them a gift. However, Roy, the character, does NOT know that when he does this, he's saving the girl(s) in question from something lewd happening to them. IC speaking, Roy is just running into them, or intentionally pursuing them because he wants to spend time with them or make them happy. IC-speaking, Roy has no reason to suspect, for example, that the doctor wants to do lewd things to the Princess, or that the massage parlor would do anything lewd to his childhood friend, or that the knight girl is dumb enough to follow any demands from the thieves... So on and so forth.
Furthermore, he has no reason to believe that there's a hidden camera network that spans the capital the way it does. That's something we, the players, know and find out about, but which Roy doesn't know anything about.
Sure, the game could have had him be suspicious of what's going on anyway if they really wanted too... but there's nothing narratively wrong with the fact that he's not. Most people wouldn't believe that the girls are dumb enough to end up in some of the situations that they end up in. Or that the mage they worked with for year is a complete dick that would cuck his own party member. Etc.
As for the other bit... Lust is a bit complicated. It's not really lust that sorta helps the Demon Lord revive in the Harem ending. It's betrayal. It also doesn't happen because the girls are particularly corrupted, but because Roy was greedy in the first place when he doesn't have the ability to keep up with 4 Nymphos. And yes, they all have nympho-like tendencies, and there's no way that any man that doesn't enhance his/her own sexual ability with magic could keep up with that. There's also the greed of the townsfolk that's involved too. Basically, I don't think lust factors in much. If it did, just having enough horny teenagers somewhere would cause demons to spawn in the setting. Not to mention that the girls that aren't married to Roy in the good endings end up very lustful anyway and there's who knows how much depravity happening in town... and still the Demon Lord doesn't revive.
Granted. I could be wrong, but I don't think. I think that there's a need for something truly extreme to cause revivals and/or the appearance of truly powerful demons in the setting. Which is why only the Harem ending has those sorts of consequences. Though that's also likely related to the fact that it's Roy that's the one that's betrayed.
In the end though, I DO agree that there could have been more to the game in a lot of ways. In some cases, like the hidden red-light district, or the bunny-girl place... and more tbh, it feels like the game is unfinished. Or like they had ideas that they had to cut out, but still left hints about them, etc. The game could definitely be improved, and it could definitely explore a lot more than it does... But the same can be said about a lot of games out there.
