Here in California our primaries tend to have many different ballots. When a voter checks in we verify the party registration records (and here in California voters can be independent of any party) and hand them the proper paper form ,,, or ... if they chose to use a ballot marking device, that device is configured to present the proper ballot to the voter.
All of this is done with human oversight backed by paper registration records - voters don't get to pick which kind of paper ballot they get and they are not allowed to muck with the machines to chose which ballot they will vote.
California does allow a lot of registration changes to made at the voting locations, but that generally involves a phone call and interaction with people at the central county clerk's office.
I'd also mention that a lot of people who have various physical issues - such as bad eyesight, or my issue with holding a pen or pencil - prefer the ballot marking machines over hand marked paper.