Are you in the USA? Every Amazon return I have done is they give you a QR code and I drop it off at a UPS store. No printing required and UPS handles the packaging.
Amazon has many faults but returns have always worked well for me.
I guess their systems aren't quite as smooth here. I'd still be quite annoyed to have to go to UPS in my free time to return something I never ordered.
Amazon has many faults but returns have always worked well for me.