It's simple to establish that rural delivery has a higher cost to the USPS than city delivery does. As you've pointed out, cutting delivery days to rural citizens also bears a high cost in the view of those with diminished service.

It seems the exceedingly sensible thing to do would simply be for the government to subsidize delivery to the costliest areas. Unfortunately that would mean taxpayer dollars supporting the USPS and that's an idea that's seemingly untenable to rural communities.

Hopefully a solution can be found in all of this. I certainly can't see one, but I'm hopeful that it'll find a way.

Maybe people in rural areas can pay for the value they're receiving?

Why is mail important? Are people sending letter? Or is that they're getting packages delivered? If it's packages they can have it delivered and actually pay the cost instead of asking other people to subsidize their lifestyle.