How well does it work for people with motor disabilities? Vision disabilities? Does an X mean a choice or they crossed out their choice? What happens when the pens run out of ink? What if they can’t read English?
Helpers? What do you pay them? Can they understand that dialect of that obscure language? Do you trust them not to lie about what they’re marking on the ballot for someone?
The truth is electronic voting machines have upsides. Having the system fill out the ballot which the voter then hands in seems like an almost ideal use to me. It’s totally verifiable but can help many people who wouldn’t be able to vote without help.