Serious question, so DuckDuckGo is not good enough?
I think they stopped using the Yandex index at some point and solely used Bing's index. This may have been the cause.
I tried kagi some time ago, and I liked it a lot for similar reasons as the author. It has everything which made DuckDuckGo such a joy to use, ánd reliably good sesrch results. I also love the filter site and boost options, and the fact that the most used are shared on a "leaderboard".
The part I didn't love was the (understable, but annoying) need to login. This is especially a pain when you use a lot of different devices, delete cookies and friends regularly or use private browser windows. I tried using the method where you need to supply the ligin token manually, but, if I recall correctly, it was a painful experience because once you logged in elsewhere it would change, so it became an effort to keep the token in sync manually on all devices.
Need to login will repel a lot of people who would test quality of Kagi search otherwise. But they want paying users, not lurkers.
Elsewhere, you are associated with a profile, both before logging in, and then if ever logged in, that association persists logged in or not. One of these feels more honest.
I know people here absolutely love Kagi and would defend it to the death, but I cannot fathom paying a subscription fee for a limited number of searches.
I'm guessing that I just don't search the same types of topics or questions that many others here do, because the complaints about DDG are foreign to me.