It is possible to do a more complicated voting system without electronic voting, and I'd be fine with that.
There are a lot of things someone might try to achieve by attacking a voting system. They might try to change the results of the election. Maybe they'd be satisfied casting doubt on the legitimacy of an election. Or maybe they'd just like to steal away some more detailed voter data than is intended to be public.
A machine updating and displaying tallies in real time as votes are cast would leak information about who voted for who, compromising the secrecy of voting. Maybe a party sees things aren't going well for them at a specific polling station and start doing some sort of voter suppression there. Or even maybe they see they are doing pretty well at a specific polling station and increase GOTV efforts in that area.
A compromised machine might display, print and report the correct tallies to local election officials but send modified tallies to Elections Canada. This might be caught with paper backups but then you'd just get a bunch of headlines about the election being hacked which would be a huge drag on people's faith in the system and enormously damaging on it's own. And of course the paper copy isn't fool-proof either. What happens if the party that won the electronic vote starts trying to discredit the paper ballots to hold onto victory?
Ultimately you'd end up relying on the paper ballots anyway, so you might as well just do that from the start. In a best case you save a little bit of time, and even then it probably doesn't really take that long to tally up the ballots at a single polling station anyway. In a worst case you get an incongruence between the electronic and paper results, which at that point shakes faith in the election at best, or causes a partisan split on which result is legitimate at worst.
"But remember: the fact
you are not paranoid doesn't mean
they are not out to get you or compromise your system." -
Cryptography Engineering