As the entire world has now seen, these century-old voting devices are ridiculously inadequate for 21st century elections.
Most voting machines used in the United States are really just glorified mechanical adding machines.
They're also often certifiable antiques. In some cities, broken machines must be cannibalized to keep other machines working because no one manufactures replacement parts anymore. And these machines do break. As the various mechanical linkages and components wear and lose their once-precise geometry, the possibilities for overcounts, undercounts and jams increase. Regardless of whether you think that voters should have been able to figure out the ballot, clearly, many did not.