Sinclair's modern day successor could be Eric Schlosser, author of Fast Food Nation. Schlosser has famously criticized both the fast food industry and the 'reformed' meat packing industry that supplies it.
As Karen Olsson wrote at Slate:
Today it's Eric Schlosser's Fast Food Nation that, like The Jungle, documents the problems of the meat industry, but without depending on a dramatic narrative. We now prefer our exposés to come with figures and footnotes, not melodrama—Schlosser's book still weaves in moving human stories to illustrate the impact of industrial development, but as nonfiction it has a rigor and range that The Jungle lacks.The meat packing industry certainly doesn't see it that way. At the 100th anniversary celebration of the Federal Meat Inspection Act where Sinclair's The Jungle was praised, AMI President Patrick Boyle was asked to compare Sinclair to Schlosser. Boyle said, "Despite the progress the industry has made in the past century, writers have not made as much progress."
I guess time will tell.