If anything it's the fact that the ntr content is skippable that's lead to this game's success.
That helped, yes. But it's also the fact that you've got an opponent to outsmart. To use a good example of why a game needs a story, take the infamous Big Brother. At first, the point is to stay one step ahead of your rival Eric, but when people complained about him (no idea why, it was so badly implemented he was pretty much a non-factor), he got written out and suddenly there was no more story. So what happened? The story devolved into a "let's make a porn" and interest in the game went down, because it was a non-story. But here there's the constant "threat" that makes an interesting story.
There's a bunch of games out there that start of strong story wise, but then lose their focus. Instead of having an overarching storyline, they're just "bang all these girls" and once that's done, they have no more idea on how to go further, since that's pretty much the story. But since the story here (getting rid of Hunter) isn't tied to sex, there's a lot more freedom.