The "In" thing

Back in 2016, it was briefly fashionable to feign interest in at least some of the places that voted for Brexit and Trump and argue that people with so-called progressive politics ought to think about their problems. But in some quarters, the “in” thing is now a sour, dismissive attitude to millions of people and their supposed complaints. (The Guardian.)

What is the "in" thing in the passage above? Does it refer to "to feign interest in at least some of the places"?