It was 90% Armenian in the 1920s; the Azerbaijan SSR promoted immigration of Azerbaijani in the region between then and the 1980s, but it never went below 75%.

Yes, which happened 30 years ago, so there's an entire generation that grew up with the borders we have today.

We don't want to go back to the borders of historic Armenia for the same reason we don't want to go back to the 1988 borders — it's history: https://en.wikipedia.org/wiki/Armenia#/media/File:Arshakuni_...

30 years ago isn't that long - there are still people alive in Azerbaijan who own property deeds for houses in Karabakh, and who were born and grew up there. At the time there were 684k displaced Azerbaijanis (UN number), most of which are still alive today.