Some new movies really get it, at last: “Eighth Grade acknowledges the extent to which our emotions and relationships are now mediated through digital channels without coming across as alarmist. That doesn’t seem like it should be rare, but it is. It’s not that we don’t see people use computers and phones on film and TV. But characters don’t spend nearly as much time on them as we do in real life — unless they’re part of a cautionary tale.”