Did you try complaining online? Because the Postal Service is in no way unique in this regard. Lots of companies make you wait on the phone for long periods of time.
I strongly suspect that’s done on purpose. They want you to use the much cheaper online option.
And that’s not always a bad thing. I had a problem with a lighting fixture recently. I called the company, and got one of those long-wait messages. Then I went online. I got a “Live Chat” person in seconds. And I had my solution in a minute.
Side note: I’m an old guy. I still like the phone better.
Interactive chat over phone any time.