Can you be more specific? I exclusively use Kagi, and I am a heavy search user. I have not noticed anything like what you are mentioning.
Since Kagi became Google for my purposes, I started using Google again. I don’t have much motivation to curate the customization features personally.
I would imagine that it could depend on the general type of query. As a developer I definitely noticed a decline in quality.
I’m quite privacy focused but for whatever reason don’t care if Google knows that I want to know how to write a helm chart or eat pasta later