Agree with others - being able to have a proper conversation. Add to that being able to speak/write properly. It's all acronyms and 'text talk' now.
Manners in shops, restaurants and public transport. You often see people sitting together at a table but they're all engrossed in their phones. Or having a loud conversation in a quiet carriage or when someone is trying to serve you.
Peoples ability to go a short while without yakking to another person. I often see people with a phone wedged between shoulder and ear while doing something else eg pushing a pram, carrying bags etc. Gone are the days when it would have to wait a bit until more convenient to have a conversation.
Common sense is another thing disappearing. The amount of people who just have to text or call while driving or some other risky activity.
People enjoying the moment. I like seeing old photos of people watching an activity but now it's a sea of arms and mobile phones being held aloft to record every moment.