I think the "original experience", whatever it may have been (and I strongly suspect there's more nostalgia here than actual worse results) would be very quickly overrun by modern SEO methods / tactics.

Kagi can be "better" than Google (for some very narrow definitions of better) because they basically don't have to think about SEO at all. They're small enough that nobody does SEO against Kagi. If their algorithm is sufficiently different that typical Google tactics don't work on it, even if it's much more naive because of that, Kagi wins.