Popa and DaMoshe are correct; the history of klal Yisroel in the times of the Megillah is irrelevant.
Look, I sympathize with you in your difficulties finding a shidduch for your daughter (I’m assuming). I think you’re being unfair to the shidduch organization(s), though. With limited resources, they’re going to focus on the demographics with which they will have the most success, and they obviously feel that they don’t have the resources to be successful with Sefardim.
There’s most definitely a perception that Ashkenazim have different cultural norms than Sefardim, although that will likely change over the next several generations.
As others have pointed out, you’re most likely to find success through a shadchan who knows your child and can suggest shidduchim based on his/her personality and level of frumkeit rather than a stereotype.
Hatzlocha, and may you soon post in the Mazel Tov! thread.