OK, put it this way. You found parcel post to beat UPS and FedEx about 75% of the time on price. But that isn’t about beating price. That’s USPS fixing the price by legislative fiat.
To clarify by example, using food stamps beats cost 100% of the time. But somebody pays the difference. The fact that USPS beats UPS and FedEx on price is meaningless if it isn’t a market.
Not to my bank account. And for over 40 years the USPS was a revenue neutral government agency getting no tax dollars, and competed head to head with UPS and FedEx while delivering to every address to the US which FedEx and UPS don't do. So, the whole bashing of the USPS as some bottomless pit of waste is pretty lame.