90% of email sent today is encrypted between servers but even if it’s not, it’s probably 1000x harder to intercept an email than a fax.
You could impersonate a telephone company worker, twist a speaker to a phone line, and literally record the noise with your phone to get a reproducible fax image.
Email is going to be a lot harder. A lot.
There’s barely any analog phone lines anymore anyway so you could say that probably made fax more secure, but that has nothing to do with fax being inherently secure. It’s the opposite of that.
I love the idea of taking on a monopoly, but I don’t like that, without regulation, it has a low chance of success, and the consumer gets to suffer as the monopoly fights back.