The doctor likely has a private practice, so without the heinous pressure of working in a hospital and all the money that comes from being part of the medical industrial complex, its no wonder the doctor isn't depressed.
Well, they probably never bother to reflect on their own actions, nor the backdrop dumpster-fire we call society. That, with the rapidly approaching line-of-no-return heating of ocean water is enough to realize Humanity is a pox upon the Earth, and yet somehow we are supposed to reconcile these feelings and our very existence and desire for personal fulfillment in the face of overwhelming evidence that we are mostly powerless in the grand scheme of things.
So yeah, stupid people and narcissists are generally happier.
I won't pretend that it's easy, but people can be in a decent state of mind while acknowledging these issues. That's how most people live. You don't need to be stupid or evil to be happier. Being stupid and/or narcissistic bring their own problems too, so that's not necessarily a recipe for happiness.
Because most people have more immediate and direct issues to tackle in their life than being philosophical about society at large. We can't all be Diogenes.
You need a certain level of comfort and safety to be able to start worrying about shit like that.