I suppose the main thing here is specific preference. It's basically impossible to account for all possible preferences, so I only account for one preference. My own. I try to give players choice in how they treat the girls, but sometimes I end up without the time I need to make literally every part a choice, so some actions come packaged with other actions. I've had comments from people who don't care about masturbation scenes, or maybe lesbian scenes, or cunnilingus scenes, but they love BJ scenes or whatever. At the same time, I'll get comments like yours which are basically the opposite. I can't really please everyone, but I can do my best.
That said, it is very much a male dominated game, and whilst lesbian content will continue to be featured throughout the entire game, with Cassie and Riley just being the start (Assuming the player enables lesbian stuff), overall it will all be central to MC, so dick will be showing up in more scenes than it doesn't tbh. Also, technically all sex scenes are actually avoidable, just not if you also want to actually persue the girls. Even then, most of them have a choice of some sort I think.
Regarding the idea to have Cassie and Riley become a couple, this is "sort of" planned. The eventual plan is that assuming the player enables lesbian stuff between the girls, he'll end up basically being the head of a big family where the girls are free to like each other as they will. (Though since canonically the only non straight girl is Cassie, this will take time.) Outside of that though, if you don't persue Cassie or Riley in any capacity, I did plan to have it implied that they got together through their stats and a couple of other hints, but I don't plan to actually explore that possibility from a content perspective since generally if a player is totally ignoring a girl, they don't want to be fed more content of that girl.
Only other thing I can mention is that the next update does have a lesbian scene, so there's that. The Cassie and Riley duo isn't one I'm gonna be breaking up, regardless of whether it's sexual. I'd love to be able to make a route where you wingman Cassie to get Riley if you're only interested in them in a way that makes that an attractive option, but since I'm just one guy making the whole thing I have to set a limit somewhere for what I can actually achieve. I'm already stretched pretty thin with the current content. If I ever got a team one day though, that's exactly the sort of thing I'd be making possible. I love games that account for that kinda thing, but there's a big reason almost no games do it, and it's time, unfortunately.