Look, I love my iMobilePersonalComputingDevice, it does an unbelievable number of things pretty darn well. But as a phone, it sucks. The sound is terrible, the form factor is less than ideal for a phone conversation, the connection can be spotty. For a 5-minute quick check in it's fine, but I had a friend call me yesterday for what turned out to be a 2-hour heart-to-heart about the meaning of life, and it was excruciating.
Yes, texts and other media are often superior to voice. But part of the reason millenials don't like to call is that the phones are terrible. Given the design constraints inherent in mobile devices, that's probably not going to change.