The sex scenes DO need to be updated, and I think I read a post on Steam about that being on their to-do list. In terms of the world being bigger or more open, etc.. it's a small team working on a fully 3D game. Sure, one dev or a small team can handle a more open world on the Renpy engine with no animations and mostly text and still images driving the story, but as far as 3D games go, this game has a pretty solid foundation in the sense that it plays pretty well compared to even some of the top 3D games out there in its style. That has to take an insane amount of work to get right in comparison with most of the other VNs you see on here where they add a bit of a text and an image and set the scene for you.
I also think they won't add too much in terms of fetish stuff because they are in the public eye more than most of the other games here. I might be wrong on that, but House Party has been covered by a lot of mainstream streamers and news outlets, and if they get too crazy, that may stop, because those types shy away from anything that might put THEM in a bad light. They're also adding the Game Grumps, and I would assume they don't want to put something out that might cause controversy in terms of what they are being associated with also.
At the end of the day, I feel like you have to appreciate this game for what it is. The devs more so focus on stellar graphics and game-play rather than trying to accommodate kinks or add taboo content (though they do fringe on some kinky stuff sometimes). Sure it's got sex, and a decent amount of it, but it's very clearly not the main focus. Most of the complaints I've seen of this game is "needs more sex, needs more kink, needs more depravity", but it's just not that kind of game. It's a very fun game, unless you don't enjoy playing 3D video games in general and are just looking for a quick wank. In that case, I can totally see how it falls short. I find the stories funny, the combat is fun, and it's nice to get a break from just reading wall and wall of text and making choices and actually have some REAL gameplay. No other adult game even really offers that.
That being said, you can do some pretty cool things with the story creator, and I've seem some pretty good custom stories that are much more perverted than the main story line, so once this game polishes up, maybe we'll see more there. It'd be kind of cool if one of the better Renpy writers used the HP engine to create something, then we might get the best of both worlds, but I don't think anybody's going to convince the HP devs to get kinkier and more perverted with all the success they've had doing it the way they're doing it. Sure it's vanilla and tame for THIS group, but that's not the case for the mainstream.