zahavasdad,
You are completely missing the point.
No one is saying we shouldn’t use smartphones because people got along fine without them for thousands of years.
The point being made is that it is rude to take out your cell phone while being menachem avel.
Ayyyy, but you’ll ask, maybe that guy was waiting for an important call, so maybe it wasn’t actually rude?
To that, DovidBT responded: “People managed to deal with that for thousands of years without carrying phones with them everywhere they go.” (i.e. he can wait a few minutes to check his phone, or if it’s that urgent he could step out)