Honestly, it's just isn't a game for you then. For me, I'd say it got better and better, but for what you said, for you, you'll think it's gotten worse and worse.
For me, it's worse and worse. Asian women in these games are almost invariably silly and childish, and here we have 2 of them unavoidable. Whatever you think of the characters, I think 7 mandatory is generally a bad idea. I don't mind being forced into content with a character I don't want, but when it's a bunch of characters it just becomes tiresome.
Would having to make more branches of paths be more work? Yes. The other option is simply make warnings when you refuse someone like:
"Not interested in Shizuka (this also loses some Asami content)"
Maybe with that choice someone doesn't like Shizuka, but goes along with her because they really want Asami. For someone like me who has no interest in either, perfect. Most of their content is gone, I throw some dick into Asami on occasion but it wastes less of my time.
Also I reflect that it's not too late. Even in future updates you could have "I think maybe we shouldn't be doing this (ends Shizuka content)".