In terms of popularity, reviewing Medicare plans during the open enrollment, going on now, ranks right up there with doing taxes. Retirees on Medicare view healthcare as their most burdensome expense. But they are less likely to comparison shop for Medicare plans than for their groceries and gas, even though plan shopping would probably save more money. Deciding on a Medicare Advantage plan or deciding to switch to traditional Medicare, with or without a Medigap supplement, is “overwhelming, scary, and has consequences, so we put it off,” said Bart Astor, a spokesman for the insurer WellCare Health Plans, whose nationally representative survey quantified just how much retirees dread Medicare enrollment. Selecting one path over another also necessitates predicting the impossible:…