How crucial is technical fit in hiring engineers?

Whether you were on the hiring or candidate side, I'm curious to hear your thoughts/experiences.

Let's say the company uses Node, Angular, and MongoDB:

Candidate #1: Above average Senior-level Engineer with matching background in Node, Angular, MongoDB.

Candidate #1: Excellent Senior-level Engineer, but background is mainly in Ruby, React, and Postgres.

And please contribute any other of the countless permutations! Would it be a different situation for Python-to-Java (or vice versa)?

Thanks!