A different kind of question.

Choco, You already answered your question, well, within your question. No need to change or think to hard. If you're kind at heart, be so. You weren't what they were seeking, but then again, they weren't what you're seeking.

Simple Choco, it's all based around attraction. It's like when large amount's of girls say they want a sweet guy and then go for a bad boy. They know what they SHOULD be attracted to, But they just aren't. Girls(The average anyways) want to have fun, I imagine at some point in the dating you get complacent and start to become more 'relaxed' put less effort into truly dating them. Which is fine mind you, But it's not exciting. Meaning in short. You're a good guy. But not a "Hot and Exciting" guy. Just keep doing your own thing, my past few girlfriends have been too immature and it ended due to this. The infatuation, the excitement of love ends, and that's what matters to them. It's all apart of life. Keep your chin up about it.

I know incels, some conservatives, and traditionalists would have something to say about those women. Personally, I'd just say cultural norms relating to dating has changed and is changing. As you are demi-sexual, maybe you give off vibes suggesting you'd prefer something long-term while the norm—seemingly—is that during x to x years in your life, short flings are preferred. Gotta be energetic and wild.