I don't think it's right to co-opt and despoil that name of doubtless many real people, so if there is a pushback against using "Karen" as an insult then I'm in favour of it. That said, this is first time I've seen anyone else say anything against it. Perhaps I also can't keep up? ;-)

Yeah, I'm not, like, put out by that one becoming verboten, I'm just surprised at the sudden change.

It was always a bad shorthand. The word you are after is “busybody,” perhaps with some preceding adjectives to indicate malicious intent.