Nothing is going to measure pencil marks perfectly, but scantron technology is decades old. Sloppy pencil usage wouldn't inhibit manual inspection of paper ballots, e.g. during a recount, but one does have to define some expected threshold of competency for voters using the ballots.

While probably scary and a non-starter for some have often wanted a key stretched hash of a voters id number/vote/salt as a public record (possibly also stamped into a blockchain) and able to be checked by the voter holding the salt and no one else.

Once you put a ballot paper in a box you have no idea whether it was properly counted or lost.

There's the inevitable issue of cryprographic advances and forward secrecy, which wouldn't sit well with some people for fair reason, anonymous voting is a cornerstone of democracy. Personally wouldnt mind my vote being public a few decades after the fact but not before then.

Electronic voting has a bad reputation here but there's certainly room for improvement on paper only.