Sorry, I used words specific to gamedev (and usually in french), so I'll detail a little more (just ask if you don't understand something) :
What I meant by core gameplay loop was "What is the player doing?" not the themes.
As I understand, the main actions players will be doing is raising happiness. For now, it's only raised by talking, and the events are in reaction to how they are succeeding. It's not a huge problem in itself, you only have to make enough content for that to become interesting. But rather than a list of 15 choices, with the best staying the same everytime (talk about cars, computers, food,... is only interesting the first time you pick them, the following will be the most points), you should try something else.
For example, most of the dating games will have it the other way : players will only have the option to talk with them, then the girl will pick a random subject. Then the player will have the choice between a few options, giving them more or less points. It's not revolutionary, but it feels more dynamic than picking the same thing over and over.
Next is happyness decay. It doesn't feel good to have to keep talking to them only to maintain happyness. If you pick the previous example, that will resolve itself, but I would suggest adding another layer :
You could improve on the handyman (or handywoman) part of the game by adding checking-out their appartment. You do that as an action, and will be able to prevent problems in their room. That has two advantages. The first is that you can make a harsher mood penalty when there is a problem in their room (like - 10 / day). The second advantage is to be able to add more high lust events while you spend time in their room (Cally might want to have you if you come there without reason, or you can find that Nicole has a hard time and help her).
There is also the money. I know you probably have plans for that later, but for now, paying the repairs with your own cash is wierd, wierder when you pay a weeks worth to repair only one room. If you want to keep money it in the game (with Guiliana's loans) I would suggest removing repair costs and weekly cash (you can just say it's used for rent/food/bills and only take into account spending money) and using it to improve your wife's happiness/corruption, and buying gifts for the girls. It's not a huge problem, but I don't feel like having a job that's asking me to pay so much is interesting
To improve the UI a bit, you should look into making buttons more dynamic (I don't really know how Ren'Py programming works, only seen other projects). Your button could be normal color when the girl is there, grayed out when she isn't and red/pink when there are noises coming from the room (NTR, inviting someone over or something unrelated), or if you want them to click the button before knowing what will happen, you should send them back to the girl list rather than the corridor menu if nothing impactful happens.
I would also suggest making picture buttons, selecting a girl is better when you see her face rather than her name only.
Finally, that's only my opinion and examples, I don't want you to feel like I'm hijacking your game ^^
Sorry for the wall of text : I like your videos and see good potential in the game, but if you try to make something that's above a Visual Novel (ie with gameplay), you also have to take the user experience into account (UX), you can't rely on the fetish alone
