I actually don't think this has been a huge problem in NZ politics in recent times. When Key and Ardern came into power, they didn't do massive "policy bonfires". They kept most of the major projects currently in progress, didn't mess with too much settled policy, and generally where they wanted to make changes, either did it through careful reviews or just made some tweaks. There were a few exceptions for headline policies (e.g. the tax cuts that Labour cancelled when they got into power), but for the most part we haven't seen the massive reversal of a huge number of policies we're seeing this time.

It seems like polarisation between left and right might be growing, which is likely to lead to these reversals, so the policy "ping pong" might continue and get worse as governments change.

I think this is just a symptom of our general move away from the larger parties. Smaller parties tend to (though don't always) have more extreme views. Labour and National are pretty close in policy, but when you add Greens on the left, they negotiate for stronger left-leaning policies. Then perhaps it would be ok if the policies were outside National's normal field of vision, but then you throw in Act and NZ First and they each have things that are key to them lying outside the normal box, which they negotiate for.

There is also a worldwide resurgence of further-right wing parties, that thrive on the divisiveness that instant worldwide communication encourages.