You're right -- the concept is great :). Last time I got an ESTA, however, the site was somewhat byzantine, chock-full of confusing legalese and the response was slow. Comparatively, to get into Europe for 90 days we just have to arrive (https://www.safetravel.govt.nz/travel-tips-travel-europe) -- same goes for Canada.
However, after checking, it does seem like the site has improved a lot. It's been a while :).