I think as well, supporters of New Zealand policy haven't necessarily thought about how reliant it was on the rest of the world taking on part of the responsibilities of the NZ state for it. Lots of Kiwis abroad, I think I read somewhere the majority, have citizenship or at least a long term visa in their country of residence. But plenty didn't.
Those on shorter term visas who weren't able to get back in were reliant on either overstaying, going to wherever they could be taken as a visitor or on other countries making provision for NZ citizens to stay longer term, as a direct result of NZ government policy. That's actually quite extraordinary.
The UK for example introduced a provision where people whose visas were expiring but were covid stranded could stay. That included people from lots of countries in lots of circumstances, sometimes as a result of UK policy too. It has also extended to New Zealanders who would legally have been allowed to travel from the UK but couldn't get back into their home country.
Essentially it was the UK state stepping in as the New Zealand government abdicated responsibility. Anyone who's had many dealings with the UK Home Office will know just how badly another party has to be behaving for them to look like the more humanitarian and responsible option in comparison.
This is NZ goverment guidance for citizens in the UK, and it's actually quite amazingly entitled.
www.mfat.govt.nz/en/countries-and-regions/europe/united-kingdom/new-zealand-high-commission/living-in-the-uk/covid-19-new-zealanders-in-the-uk-frequently-asked-questions/
Options are limited, you should take steps to stay safe where you are, we aren't going to give you any money to pay for the consequences of our policy, if you can't afford to safely shelter see what your family and friends can do, get in touch with the UK Home Office who have accepted temporary responsibility for keeping you while we refuse. It's all basically saying you aren't our problem, someone else deal with you.
Now I'm actually glad New Zealanders stranded in the UK can at least maintain legal residence. It's a good thing. In a pandemic, I wouldn't have wanted the UK government or really any other to waste time and resources trying to force NZ into accepting their own citizens. But equally, NZ are lucky that other countries have been willing to do this, to keep or take in the citizens they refuse to have back or at least not to actively try and remove them. Had the rest of the world declined to cooperate, the charade of the past couple of years couldn't have happened.