The issue with DND is that it blocks all incoming notifications as well. That's not what I want at all times. A push notification doesn't take over my device like a phone call does, and I want to be able to get notifications from chat or email even though the sender isn't in my white list.

The whole system underlying phone calls is broken in the same way that the internet is, i.e relying on a level of trust that just isn't there. There is no argument I will accept that will persuade me that any device should be able to contact any other device at all times. There is no need for such a synchronous type of communication, now that we have had the internet for over 40 years.