The simplest argument against government run services is that eventually, the people you don't like will be in charge of them
You will have those same people you don’t like running private enterprise, but CEOs have much longer terms than postmasters general.
My choice to go with this provider or that one has 100% of an impact on me. There is no creative destruction going on with the USPS.
Voting is the most minimal way to participate democratically. Much more meaningful are advocating for your needs to elected representatives, speaking out publicly, and organizing/attending demonstrations.
But if you want to give up democracy to live under a dictatorship, certainly don't pretend that you actually speak for anyone other than yourself.
Please don't do the Reddit thing. The argument wasn't "we need dictatorship", it was "it's easier to switch commercial providers than governments if you're unhappy".
This is because they have a government protected monopoly. Cities like Chicago and Baltimore and NYC used to have dozens of competing utilities before the government began granting charters that gave one firm an exclusive right to provide power, gas, or oil.
The difference here is that it's not profitable for UPS to piss off its customer base. A CEO of a privatised postal company acting in his own rational self interest would produce far different results than Donald Trump acting in his own rational self interest.
And even if the CEO didn't produce good results, I could mail my letter using another firm. With USPS, this is not possible. They have a legally protected monopoly on the delivery of letters. No one else can do it.
Voting is accountability. You’ll have to find another time to discuss every other thing that’s wrong with our government, because right now we’re talking about a service being purposefully degraded in efforts to reduce the one of the only means we have for holding government accountable: voting.