This is life. The UK, for better, for worse, left the EU customs union. Choice made, train has gone, not coming back. Live with it.
No use blaming shops if they are inefficient at the complications of trading across the barrier. No doubt, if it’s a core part of business, they will go to the wall, or if peripheral to the business they and you will live with it.
Works both ways. Living in France, stuff from the UK has to be sent so La Poste delivers. Or I’m not buying. They send an e mail with the tax bill, I pay online, I get a code as proof of payment, and postie captures it to his machine. Charge about £2. That I live with, if I NEED that item. Otherwise, trade within my customs area.
I’m still waiting to see if the UK cheese industry collapses from my loss of custom.