Well it's not is it. How many lorries, drivers, planes, deliveries enter NZ each day Vs the UK?
Whether it's correct or not, NZ has adopted a zero covid strategy. No other western countries have, apart perhaps for large periods Australia. Obviously it's just a massive coincidence that these are countries with no land borders and hundreds of miles from anywhere else.
Again, we can debate whether it's the right policy or not but quite obviously it's easier for NZ to implement it than the UK or Germany or France or Canada or almost anywhere else. To ignore that is to ignore geography.