It's already been privatized. That's the problem.
It's one of the few Constitutional functions of the Federal government that they actually should be performing. With exceptions, of course. It's not 1789 any more.
I delivered mail for five years 1969-1973 as a summer temp to pay for school. I wore the pony under USPOD and switched before I finished to the stylized eagle of USPS.
Certain functions, like first class mail to every mail stop in the US should be returned to the Post Office Department. Yes, I watched the stupid Kevin Costner movie. Also yes, it made a good point.
As far as the taxpayers subsidizing the last ten miles for Bezos? Screw that. Bezos should pay for his deliveries, AND if he wants to mail them under proper mail rules they need to wait for the First Class mail to go out. If not, let him buy all the trucks, drones, and drivers he needs to afford that yacht.
Flats (catalogs, magazines, Nikki Haley ads) can be privatized for all I care.
What you wrote above is what I've heard from several relatives who were/have been postal workers for many years. They might not have a problem with privatization, but they have pointed to the Constitution. Many years ago, a post office job was considered a good job. But, nowadays, they mostly deliver packages because the USPS is competing with Amazon, UPS, FedEx. To say the mail carriers are not happy now would be an understatement. Instead of delivering letters, they're mostly delivering big, heavy boxes, and the letter delivery falls behind. They are overworked. Nevertheless, the older ones stay committed to the job. They always say they're hanging in there for the pension, but often they put off retirement. It's like they belong to a brotherhood they don't want to leave. They see their job as important and take their duties seriously. Actually, Clifford from Cheers wasn't far off. (lol) In fact, that actor was used in USPS training videos. I've never watched the Costner movie. I should check it out.