Why on earth should the EU be allowed to control something as simple as a private individual sending a parcel from GB to NI. Just crazy.
The problems are from what the EU insists the restrictions should be via the Joint Committee.
IIRC the supermarkets weren't anticipating any problems, so the the issue can't be in the NI protocol itself, but what the EU dictates in the Joint Committee. All that has to happen is the EU tosses aside all the nasty restrictions in the Joint committee. There is no other solution.
Why is it ok for the EU to be able to ship unapproved items(including parcels) to GB via NI unfettered by any restrictions, but GB not ship things to NI? Unbelievably one-sided and unreasonable, then that's the EU for you.
Imagine the situation where X & Y are getting divorced, but X can do anything they want, but Y can only do anything, if and only if X agrees. On which planet would a court not dismiss that arrangement as being unfair and unreasonable?