The advantage Kagi has over Google is the different business model. Google would never for example introduce a "non-commercial" filter as it would go against their advertising-based business model. Kagi doesn't give a shit about ads and will do whatever that keeps its users paying and so has a non-commercial "lens" (as they call it). I'm not sure how good or accurate it is, but it's at least there which is already more than I can say about Google.
Kagi has a feature to prioritize or exclude some domains. Google doesn't have that despite their size, resources and decades of search experience. That makes it pretty clear to me that Google's weakness has nothing to do with experience or resources and thus a new entrant could potentially compete without either.