Unless my English skills have deteriorated horribly in the last day or so, I'm seeing Article V say that Congress either proposes Amendments or calls a convention to do so when 2/3 of the legislatures apply for it. Said proposed Amendment is then ratified by 3/4 of the legislatures or by conventions in 3/4 of the states.
Except for one Amendment, the 21st, they are typically passed by Congress and ratified by the state legislatures. In the case of the 21st Amendment, which specified in its text that it be ratified by conventions instead, the voters elected delegates to the Ratification Convention.
So while the Amendment process is not a direct ballot issue, the voters can and do have the power to directly effect a change in the Constitution if they want it enough. They need only overwhelmingly pressure the political office holders they have, or elect new ones specifically for that purpose, or insist on Amendment by convention.