"Karen" started off as a useful way to quickly shame people who verbally abuse / speak rudely to service workers. But now "Karen" is used for anyone who speaks up about anything wrong in day-to-day life.
"Complaining that your scheduled takeout order is 15 minutes late? KAREN!"
"Complaining that your neighbours are playing loud music at 3am? KAREN!"
"Complaining that there's a spill in the entrance that someone should be made aware of? KAREN!"
There are legitimate reasons why people should complain to service providers, businesses, managers, etc... "Karen" has evolved into this catch-all term where anyone complaining about anything is "punching down", "entitled", etc. It's ridiculous and now being used as a defense by actual assholes / lazy fucks who are breaching basic social principles and who deserve to be told off.
And before you call me a Karen (you smartass) I started my career in retail and I've dealt with rude as fuck customers: the original "Karen" concept. Those people are assholes and deserve to be shamed. But 90% of "Karens" these days are just normal citizens who are trying to deal with actually entitled people who give zero fucks about their job or the people around them. It's annoying and counterproductive and I'm ready for this overused term to fall out of the modern lexicon.