Facing a fierce public outcry, the U.S. Postal Service is “suspending” its sudden cost-cutting moves — tossing out high-speed sorting machines, uprooting collection boxes, reducing Post Office hours and eliminating carrier overtime — that have slowed mail delivery and threatened the on-time delivery of mail-in ballots for the presidential election.

That’s all to the good, but it’s important to understand that the changes to USPS that Postmaster General Louis DeJoy and the current administration have in mind for after the election could permanently damage this quintessentially...