I think the idea is to refuse to order items shipped by FedEx also. Which is easier said than done, firstly it might be very inconvenient/impossible and secondly you may not always know the carrier until it's too late. I know that because I hate FedEx and have had issues with them numerous times, but often it's not a choice and then later after my order was processed I get a FedEx tracking email, basically letting me know there's a 50% chance I'll have issues actually getting my package delivered successfully.

The only thing you could actively do is refuse to use them as your dispatch option.

As you highlight, receipt isn’t really your choice. You could ask for other mailing options I suppose but as a rule dispatch contracts are locked in place.