Aaron Brockett of Indochino, an internet retailer of custom-fit suits, measures Mark Papish for a tailored suit in New York, April 27, 2017.

If future anthropologists want to study the rubble of early-21st-century retail, a good place to start will be what Amazon.com did to apparel shopping in the few years before and after 2017.

The outlook for physical retailers is grim, the sector roiled by store closings, layoffs and bankruptcies. This year, Amazon will surpass Macy's, which last year announced it would shut 100 stores, to become the largest seller of apparel in America, by several analysts' estimates.