To be fair, "karen" actually started as slang in the US Black community, describing a white woman who deludes herself into thinking a normal Black person just existing in her vicinity is somehow a mortal threat to her and calls the cops on them.
But yeah, like pretty much every slang term invented by Black people to discuss racism that hits the mainstream, it got misused over and over until it lost all its original meaning. Nowadays, it basically means "a middle-aged woman does something I personally find annoying (including just existing in my vicinity)".