I can pretty much label someone a narcissist (or not) correctly up front.

That's a good skill to have as some people (especially those in narcissistic families) seem to attract narcissists.

Narcissists are often the shittiest people (as in, most woke and top level people like Hillary Clinton are blazing narcissists.)

Hillary is definitely a narcissist.

Do you think Trump is a narcissist? He is often accused of being one.

And then there are sociopaths. The worst work environment I was in was when I had a narcissistic boss and his boss was a sociopath and I ended up in the middle of some of their battles.

Sometimes people are simply insensitive and take shit for granted. Like Jo's relatives.

True. I've heard it said that narcissism is a spectrum. Everyone has at least a little bit of narcissism, some much more than others.

naming someone else's disorder doesn't really help to cope with them

That is true. It doesn't help because they will never change. All you can change is yourself.

They're a product of the time they grew up in. They're Gen X, so they grew up with texting and they tend to be shallow about interactions and they don't value immediacy or authentic connections. They take Jo completely for granted and one day hopefully in the distant future when she is no longer around to plan a holiday dinner, they'll dimly realize what they blew off because it was "boring" and they will then feel the loss.

That's a good summary of the situation.