While that's a decent premise and I agree that less than 5% of the US population understands blockchains, I would also reckon they don't understand HTTP (or HTTPS) protocols, B-trees, networks, cryptographic hashes, or even the compilers that underpin much of technology. But they're more than willing to trust these things with the entirety of their liquid assets if it spares them a 20 minute trip to the bank.
I think there would still be a group of people who don't trust blockchains (or, let's be real, technology whatsoever - like the interviewee). And they're the people that drive to booths and do their business on paper. And I'm okay with that.
However, with all of those. If there is a problem: either the consequences are not significant. Or there is a paperwork around to a problem, which includes laws and judges.
With online voting, we are deciding the judges that get to say - "everything is totally perfect with the way I got elected."
Honestly, given the fact that a significant number of people already think their vote "doesn't count" (given on average ~40% of people don't even bother) I doubt they would be more concerned with vote tampering than with potential identity/bank theft.
I think there would still be a group of people who don't trust blockchains (or, let's be real, technology whatsoever - like the interviewee). And they're the people that drive to booths and do their business on paper. And I'm okay with that.