You've missed the point. A porn game should probably focus more on the porn and less on the poor RPG elements that don't add any meaningful gameplay. It feels like busy work between very sparse CGs.
Considering that the source material of this parody/fan game has "Dungeon" in the title, with the
dungeon being what the MC does pretty much all the time, where he also meets some of the main cast, and most of the story happens, I would say that it is pretty much fitting.
As for the "RPG Element that do not add meaning gameplay", it can mean everything or nothing, you would need to expand on this. If you have suggestions to improve some features of the game, you are welcome to suggest them and I will take them into consideration!
I also do not understand what you mean by "Sparse CGs", if you were looking for the classic western-style game where each sentence has a CG, then that will never be it as I believe that is a very flawed design.
I follow the eastern style design where Characters and Backgrounds are separate, and all of the mundane dialogue only changes sprites/backgrounds, only "Special events" get their own CGs which can be viewed again in the gallery.
That is a good way to see how much of the game you have completed; In addition to that, sex scenes can also be replayed from the same gallery.
As of R10, the game features over 60 CGs (Without counting the alts) in 4 hours and half of gameplay, that's not bad at all.
Last but not least, "A porn game should probably focus more on the porn", that is something I can agree on, but where does it say this is not a porn game? Is there only a single way to make a porn game? Should we take Romance and Vanilla tags off this website and yeet the plot that gives context to the MC getting into women's panties?
This is first and foremost a fan game made by a fan, and as a fan of the series I am parodying, I take into account the characters' personalities to the best of my understanding in order to write sex scenes happening in a believable and seamless way, as I would imagine they'd happen in the original source material given different choices.
That is why in Overlord H you see nudity in the first few minutes of the game, and if I were to make a parody of Interspecies Reviewers, then you'd probably see sex at the very intro of the game.
That being said, it is not like the game lacks porn content... As of R9, it features 12 hentai scenes (without counting the ecchi/nude CGs), that is 20% of all the gallery which given the nature of the game, it is far from being few.
If you disagree with those numbers, just keep in mind that sex scenes were introduced on R6/R7, so that percentage is bound to only increase as the plot advances and even more routes get introduced.