Stuffing ballot boxes is much easier than an attack on an electronic voting system.
If you have free and independent observers it most definitely is not. If you don't have them it doesn't matter (with an electronic system you would have had exactly the same results both in Ukraine and Korea just at a much lower cost..). You'd need much resources and political power to compromise a normal election. With internet voting you'd need just a few people in the right spot (i.e. developing/maintaining the system) and some security vulnerability/backdoor to do it.
Also it's virtually impossible to guarantee both security and anonymity with internet voting.
Wikipedia has a whole article about it in the Estonian case: https://en.wikipedia.org/wiki/Electronic_voting_in_Estonia
That's both a strength and weakness of the system. The less people in the process, the easier it is for someone to manipulate the process.
That's irrespective of limiting the choices, obviously.
With internet voting we lose that. There is no way for most people to audit the system. Even if it's supposedly open source and transparent it's tricky to guarantee that the actual system is not tampered with and has no backdoors.
> Election integrity is more about the people running the election
True. But but fraud involving paper ballots is both difficult to execute at a large scale and hard to hide from other which is a huge deterrence.
Yes the electronic system can have flaws, but the old system didn't prevent the issues either. So might as well go with convenience.
People can be confident in paper votes because they can understand how to audit the result, and who does it. The best e-voting software in the world can provide that level of trust only to some engineers who know the code, and only if they can audit all the systems where the software is deployed.
It's like passwords, it can't work if part of the population has no clue why it's needed or how it works. It's even worse with blockchain, because you can't put everything on the blockchain, it needs to interact with the real world, and that's where you can cheat the system (like stealing the keys of people in retirement homes because they don't know what they are for - sure it happens with paper but it's harder to do and easier to catch them in the act).