One letter "doesn't do anything", but a surprisingly small number of letters does. And the one Congressmen "can't do anything", but usually a small number of Congressmen can sway real change. HN often advocates writing angry letters to Congress because it understands this dynamic.
You will never be allowed to talk to the people who made the fax policy; they hired people like Karen specifically to make sure that doesn't happen. The person who can talk to management is... Karen.
These systems usually settle into a steady state where the interface with the public receives an acceptable amount of abuse. I guarantee that if a few people a month did what OP claims to have done, they'd figure out how to take docs over email pretty quickly.
They usually offer "casework" services where a staffer will facilitate their constituent's interactions with federal agencies. This would probably help get the OP's specific issue solved AND make the legislators aware of the problem more generally. My impression is that agencies are often pretty responsive to these things: nobody wants to be on a senator's bad side.
And saying it doesn't is like saying "my one piece of litter won't make the park dirty". Just because you can't see the effect one instance has doesn't mean that it isn't meaningful when added all up.
Regardless it doesn’t matter in the end. Because you don’t litter, I don’t litter, vast swaths of the population don’t litter
Yet still, I routinely see otherwise nice parks around me trashed.