... whom an inexperienced hiring department entirely trust when they assure that the technologies they are already familiar with are the best fit for the company, let's hire only people who think the same?

I'm not sure if you're being obtuse. But rewriting your stack in a language no one on the team knows because someone on HN said it's a better fit for your usecase is something no good engineers/managers would think is a good idea. If a potential hire thought that was a reasonable thing to do, that would be a major red flag - a sign this person lacks experience, and any kind of business understanding.

It depends, if a potential hire suggests using Python instead of R or Java to process data, that's a reasonable proposal.