Google ~13 years ago dealt with a much less complicated search landscape where
1. Its own products weren't (as much) part of the search result quality problem. Today Google has hungry product managers from Ads, Youtube, and various AI products convincing higher-ups that their product deserves higher placement. That placement used to be sacrosanct.
2. The daily volume of AI-generated garbage content 13 years ago was probably a rounding error in today's volume
So Google was operating in a different landscape than Kagi of today. They had to do a lot less to achieve the quality they had.
I disagree that that Kagi "isn't anywhere near as good as Google was ~13 years ago". It's near. For me personally, it's better because I'm never served first-party ads.
Yes - a big part of that is that online content is so much worse than it used to be. But it became bad over time because of what Google incentivized.