As someone with a lot of experience in other languages who joined a ruby shop, imho its best use is for teams that already know and like it. Its at a few thriving companies so it wont die anytime soon, but i dont personally think its a good choice otherwise. Mostly because i think types, more robust error handling, or the wider ecosystem (ex python, js) that other languages provide offer more avenues for professional development and ways to reuse / extend language expertise.