I cannot comment on how good Kagi is - based on enthusiastic reviews here, I can only assume that its results are of phenomenal quality. Again, based on those view, one could easily imagine Kagi taking over the world. I glimpsed at their transparent stats and they are only at 8.8k paying users. This is not a bash or a critisism, but just sharing how things are different when observed from a HN lens.
https://kagi.com/stats