I agree, although the gamefied nature of the sex scenes also mean they become trivially easy and repetitive once you figure out the "trick". Almost becomes a chore.
Of course, this wouldn't be the case if each girl was unique, but as they are all copy and paste of each other you can basically use the same methods with everyone.
As for your later half: "I wish the game had more stuff to do" is what everyone has been wanting for years now. But Oni is hell bent on "adding new characters" being essentially the focus. He has been doing it for years and earning over 5k a month to do it.
It is what it is. The gameplay cycle of Rogue Like has literally not evolved at all in over 5 years. I don't think it ever will at this point.