I think any reasonable system would include both. Paper backups + digital efficiency seems like the way to do it. Maybe paper backups + blockchain digital solutions would be preferable.

At which point why bother with the blockchain?

I think the point of blockchain is that it's more traceable and secure than other open options. I would think of it less as a crypto-currency and more of a merkle tree like git. Voting blockchain solutions won't be decentralized. It's just a useful protocol with some benefits.

Which is not what you want in a secret ballot election. Ballot secrecy is an important safeguard to prevent coercion and vote buying.

There are protocol choices that still enable secret voting like monero for example.