I don't think it is. I've had times in my life when I certainly didn't constantly distract myself, and being of a contemplative type, sometimes also delved int

I don't think it is. I've had times in my life when I certainly didn't constantly distract myself, and being of a contemplative type, sometimes also delved into existential thoughts. But I didn't automatically (or generally) feel angst about it. I'm not religious and haven't been since I was 15 or so. (I don't deny possibly having something of a mildly spiritual side, but I consider that different as it doesn't require belief in anything other than various kinds of feelings and experiences being part of the human experience. It also doesn't provide an externally assigned meaning.) In times when my mental health and wellbeing have generally been worse, existential questions have also become much more distressing. So yeah, maybe for some or even many people, existential questions may amount to angst, but in my experience it has depended a lot more on my other emotional and psychological state.