Formlose Gestalt

Well, of course a prologue wouldn't work in a mystery horror story, but that's not what I was talking about. It's particularly meaningful for high-concept fantasy and sci-fi world that can be confusing to the player if it's not explained properly. Giving just enough context to make it comprehensible at the beginning, and minimize the need for infodumps when the action picks up pace is pretty optimal. In the case of your story, I simply think it could've done with a lot less info in general. I'd like it more being vague than just explaining the lore this way.
That is a good point, but if you think of it as another method of "scattering" the infodumps to keep the complexity of the world without creating the walls of info in the middle of the story it should still be worth it. I also don't like encyclopedias if they contain information actually crucial to understanding the story – as you said, it can be cool for fleshing out your world, but it can't be a primary method.
...I might also be speaking from one specific trauma of an EVN with a world that was pretty much incomprehensible because of lack of proper exposition, and with encyclopedia which created more questions than it answered. A good prologue could've done miracles for that game.

If it flaws properly with the story, I wouldn't even call it an infodump. I think when people talk about those, they mostly mean the first kind you mentioned: just walls of information bringing the story to a hold for a significant amount of time. But for this reason, I kind of feel an infodumping prologue is underutilized in VNs. You can quite easily avoid putting clunky exposition in the middle of your game by explaining the basics of the universe at the beginning. Maybe devs avoid it because it's cliched to do a narrated introductions like that, but particularly in EVNs, I feel like a lot of storytelling issues and confusion could be avoided that way... 

I was discussing this with a friend recently, but it was our consensus that Maggot Baits is one of the few eroge that could benefit from having all its h-scenes removed...  To be blunt, the h-scenes are in the way (vanilla or evil h, it doesn't matter).  
As for pacing, that's actually typical of Kurashiki when he doesn't have Takahama, Marimo, or one of his other Light people keeping him from doing what he wants.  Sora no Baroque had a similar problem.  The writing is good, the story is good, but the pacing is abominable.
Edit: I liked the game's story, but the H was gratuitous in several negative ways (understatement).

Thanks for the review. I am glad that I passed on Maggot Baits, this title isn't for me, even though the story sounds interesting.

Thanks for the review. I am glad that I passed on Maggot Baits, this title isn't for me, even though the story sounds interesting.