FYI you can “silence unknown callers” on the iPhone, just search under settings. Then your whitelist is people you have in your contacts. Maybe Android has a similar setting too, I don’t know though.
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.