I’ve never really bothered to understand it to be honest.
I was always confused how it was one entity for certain issues such as the Olympics or the Eurovision but then different for important stuff like the World Cup.
The fact that I was at war with you just caused me to be even less interested than normal.
Point of order: we cannot give Northern Ireland 'back', since the Irish have never had it to be given it 'back'. Ireland has never been a meaningfully united political entity other than under British rule.
That said, I see a lot of useful aspects to essentially treating Northern Ireland as a bonded warehouse for exporting to the EU.