On the other hand, it would be nice to know the core languages in play. I have no interest in working in Java anymore, I avoid job listings for companies that would expect me to write Java. I don't want to have to go through recruiter screens etc before I can ask someone who will know what language I would be spending the next year of my life working with

Our solution to this is that we are clear that we're looking for Haskell programmers (as in that is what they should expect to do) but we have very modest requirements in terms of prior knowledge. I made sure to relay to HR that almost nothing is required in terms of prior knowledge (language-wise) and that we should expect to teach Haskell to people instead.

That’s a fair point.

I think that in the specific case of Stripe, they specifically mostly use Ruby (from answers I found online). I may be wrong, but I assume that not mentioning Ruby is a way to attract Python/Go/C/etc. developers that might otherwise think that since they don’t code in Ruby, they shouldn’t apply.

Your main point (re: Java) remains of course.

Not to pick on Stripe, but why not say this explicitly?

"We mainly use [language X], but you don't need experience in [language X] for us to consider your application" - this is a totally normal thing I've seen in many job postings.

I agree.

Stripe is sometimes more explicit about it:

https://stripe.com/jobs/listing/infrastructure-engineer-ruby...

"Our most popular language in the company today is Ruby, and we are building a new Ruby services practice in support of this."

... but that job is also an openly Ruby-centric job.

They are massively profitable too. I'm not implying a correlation here but.....