I don't know how this "Karen" thing started. I had a high school girlfriend named Karen. She was a bright, optimistic charming girl and is now a bright, optimistic charming woman.
Decades ago "Bruce" was used to denigrate someone as effeminate. This was popularized on Johnny Carson. Parents of a son named Bruce wrote him a letter explaining the difficulties it caused their young boy. Johnny stopped. I'd like to see "Karen" similarly retired.
I feel it is unfortunate for people named Karen, even if it is a joke.
I generally don’t use it, except in references like this.