The problem with "good cultural fit" is that you need to ask some really hard questions about what you mean by that phrase. In many companies it seems to boil down to "people I'm comfortable hanging out with."

Very strong engineering teams are not necessary comfortable places, because they have members with different but complementary viewpoints. The cultural fit in this case is to be able to debate vigorously but also to be able to accept decisions and move on together. It's not that important to be friends outside of work.