She's an incredible singer, and even more amazing songwriter.
Have you ever looked at the list of the songs she has written? It is incredible.
But if on top of that, and I write that grinding my teeth, you can also act and adapt to the circumstances, act in the sense of faking - you'll have even more success.
If you "act confidently" is that acting, or is it confidence? It gets a bit blurry, doesn't it?
Some people out of every generation manage to get out of the act, and be themselves.
I get the healthy side of this, but I think more often than not, it is used as an excuse not to develop. "I am being myself" - (no matter how little I can do). "I accept myself the way I am" - is used to stay in the comfort zone. "I was born this way" - as if all those people who have improved and overcome their conditions, didn't have to work for it.
Yes, it's such a long list of big hits. And she can perform most of them herself. The life-version she does of "Diamonds" is stunning, I like it even better than Rihanna. But I'm a sucker for Sia's voice.
The best act is when you can convince yourself that you're not acting. And since most people learn how to act/fake from early age, they get really good at it and believe themselves to be the act.
The examples you bring up are true for every generation. They're made all the time, by everyone, and even crossing generations - "Don't mind grandpa being a racist, things were different back then." Excuses make life easier superficially, but do bring a ton of complications in the long term.