A smartphone is as crucial as, say, a car or a washing machine. Though it depends on the situation.
Internet access is becoming essential. At least in some countries, they are talks about making it a basic right, like electricity and clean water, and making some official procedures internet-only. And for some people, especially the poorest, a smartphone may be their only way to access it.
Considering you are posting on Slashdot, you probably own a computer and a home internet access, and maybe the same thing at work. And your activity most likely doesn't require you to be online at all times. In other words, you have the privilege of not needing a smartphone.
It is the same as a city dweller saying that a car is not crucial. He is most likely right. In fact, in some cities, owning a car is actually undesirable. But that's forgetting that if you live in the suburbs, not having a car is inconvenient, and it is basically impossible if you live in the countryside.