Because they had gone through their character arcs, it got to where you really liked them and understood them, which is the main reason why I took them out. If they had stuck around they would have been flat one-dimensional characters who exist solely for sex. Eventually, people would have gotten tired of seeing them and since with 10 established characters needing screen time I wouldn't have been able to introduce anyone have them go through their character arcs. People would have disliked the old characters and not liked anyone I added. The downward spiral of the story would have been meme worthy.
Okay. I apologize for butting in and I don't mean to sound disrespectful but as a fellow author I can't in good conscience stay silent on this. While I agree with your general sentiments about where the story needed to go (and even if I didn't - my opinion in this case doesn't matter - it's your story) HOWEVER as a fellow writer and creator you should be perfectly aware that at least half of every story is the presentation. In engineering, in science - you can sell ideas just on being good. But in art - and what you're creating is definitely art - how you present your work - how you sell it to the audience is just as important as what you sell.
For example take Dune - one of the most beloved Sci-fi of all times. Yet the whole story is largely tied to (and driven by) the fact that the titular planet Dune is a desert where they can't get enough water. Which is a completely nonsensical premise when you have space-ships capable of traveling between planets. Just mine a few ice asteroids and you solved the issue! However the author sells it well enough that when you're reading it - you're too into it to realize how stupid the premise is.
In your case - there is a simple and obvious solution that would satisfy a sizable portion of your disgruntled fans yet mean little to no extra work for you. Let the girls stay in contact but move on with their lives. A few lines with no extra CGs would sell it quite well.
Let me give you a short example:
"After the girls graduated they moved on with their life. Some went on to continue with their studies on different Universities around the country and some even went to study abroad. As bitter-sweet as it was for all of us to part ways we knew from the start that it was going to be pretty much inevitable and both me and Molly agreed that we wouldn't want to destroy the girl's futures to satisfy our needs. We stayed in touch with them of course. The joy of modern world meant that even while away we could send each other messages and even occasionally call each other over Skype/Zoom. We even had some of them visit for a weekend. But as the summer vacations came to a close and the girls started seriously preparing for their first year at Uni our contact became less and less frequent. In the end it just mostly fizzled out. [Put a girl's name here] promised to come visit on [choose a holiday] and we would be happy to see her but there was much to do in the meantime..."
Afterwards you can have the girls appear once in a while as a welcomed and unexpected cameo or simply mention it off-screen. "[Put a girl's name here] visited us over the weekend and it was sweet to see her but I couldn't stop thinking about [new hot girl MC is boning]"
My personal choice would be: include some of the more dominant girls - like Kendal - as a cameo and have her play with one of the new girls letting the MC cuck them both while the wife watches. Kendal can mention how it was fun but she's off and to call her when we want to do it again.
In the end - little to no extra work needed - except writing a few lines of text and maybe creating one or two CGs if you include the girls as cameos - yet it would seem much more believable. People rarely go full cold turkey on relationships however it's very common for long-distance relationships to fizzle out - once the people start living their "new normal" that doesn't include you. This way people would be sad that the story moved on but there would be way less people getting actively pissed at you for "totally destroying their heart, ruining the story, hurting their dog's heart and being a big dumb meanie!"
Just my two cents as a fellow writer
EDIT: One good example of something similar is this series of stories (warning you may get addicted)
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Steve the author/MC mentions every now and then (in-character) that he and his wife were attending swingers parties/having sex with other couples but since it's not the focus of the story - he won't get in the details. He does that every few chapters so the readers keep it in mind and only rarely does it actually matter to the plot but it helps to expand the character and gives him depth and makes him feel more real.
