In all/most democratic countries anyone can observe the counting of paper ballots and the process itself is relatively simple and easy to understand for almost anyone (even if not very efficiency).
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.
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.