What makes this Gen Z behavior acceptable? Chiding the next-older generation for their culture is akin to making fun of the accent of your coworker who was born in India. It's just rude.
IMO it's a form of ageism, but given that most of these articles are written by 20-somethings at Buzzfeed and the Verge, there's zero incentive for that angle to be highlighted, as none of them have personal empathy for it.