I worked in retail for years and customer facing roles.
It was/is always, always the men that act entitled. I cannot think of a single example from retail and my other areas even the 'hard work' women had a point and could be worked with.
I did have a man over 6ft try to throttle me and the police were called because I implemented something perfectly logical he wouldn't have done that way.
And another man who did their best to get me sacked by essentially stalking me.
So apart from it being sexist, Karen is in no way a helpful term for those in 'services'.
I was entitled today. Asked for a full breakfast but got a single. Sent it back because it wasn't what I ordered. Nobody died by heading beans and a hash brown on the plate. No body outlines, no shaking traumatised staff.
Sure they did a little eye roll, but I fail to see why they get to provide you with not what you ordered. If I was scheduled for eye surgery and they started drawing cut here lines on my foot I'd certainly speak up. It doesn't hurt to have a little pride in what you do, even if you don't want to do it. Most of us 'Karens' had service jobs, that's how we learned to complain assertively and politely. It's also how we learned to do well at things that are not important to us but might be to someone else.
Until all professionals can hide their ineptitude behind the shield of Karen (shudder, horrible thought) then people should just accept that asserting your boundaries, needs or rights is not entitled, as having entered a contract (bought a coffee etc) you are, by definition, entitled to what you paid for.
This concept is older than the bartering system so there's no excuse not to get it.