I found the search to be super hit or miss.
I heard similar complaints from friends that came to visit. But they were using the English version of the apps, which, when I tested, were indeed harder to use, but never a miss for me when I helped them. OTOH, I always find my destinations within the first three options when I search in Korean. So maybe it's subpar internationlization.
They lack a lot of polish. [...] some interactions are janky
I see. I guess I wouldn't know. It's not janky for me, and I think that I am so used to it that when I need to use Google Maps, or any other, I feel a bit frustrated by the unfamiliar interface that I start wishing I could be using Kakao or Naver Maps instead.