The problem with the concept of authenticity is it has to be authentic in relation to something.

For instance, if you are to insist that someone who prioritizes their physical appearance is an inauthentic individual, as many do, you're implicitly saying that an interest in such aesthetic preferences are inherently wrong at some level.

Someone might counter that the motivations behind such preferences are salient. For instance, you might argue that the reasons someone might spend time on their physical appearance is for some kind of social end you disagree with. Perhaps you argue that social relationships should be built upon deep intellectual connection. But then what about people who build it upon shared interest in sports, or video games, or bitcoin? Are those things "shallow" foundations for relationships too, on their own?

It turns out whenever you talk about authenticity of people, there's some kind of preference you're projecting. You're assuming you're the objective one.

To the extent someone might be saying these other people are not authentic humans, and that they're not being their "true" selves, I think people are being misanthropic in a sense.