I don’t believe the tourism argument holds up in the slightest either. The UK has the fourth largest number of yearly inbound tourists visitors in the world. New Zealand is 69th. Source: https://www.indexmundi.com/facts/indicators/ST.INT.ARVL/rank...
The degree to which the UK is connected to the world is just on a different scale to New Zealand. That’s before you even consider the geography, population density, and wealth distribution sides of the argument. It was always going to be more difficult to control it in the UK. I don’t think lack of will is a valid excuse either. What country doesn’t want to get back to normal as quickly as possible? Why is it that only this tiny island in the Pacific has managed to do it? Is every single other country is simply that incompetent? It just doesn’t make sense. There has to be other factors involved.