UPS and FedEx charge too much, and I do regular media shipping, so No, do not abolish them. If I could direct all of my tax money that goes to the US military into the USPS I would do that. Give them more money.
"I personally use and like a service" is a different statement than "it's in our national interest to continue gifting that service $10b per year in subsidies and benefits".
The other is a policy position that apparently a lot of people want to discuss.