You are missing a lot of context. The DRW tech team has a lot of ex ThoughtWorkers - many of the best got tired of traveling around for consulting assignments

You are missing a lot of context. The DRW tech team has a lot of ex ThoughtWorkers - many of the best got tired of traveling around for consulting assignments and were snapped up by DRW. Jay was a very respected dev when he was at TW (we worked on a project together- hi Jay!), and if I were trying to hire him I would be hiring him specifically so that he could raise the bar. Adding Clojure to a java code base is trivial, especially given the calibre of the DRW team. The idea at TW when I was there was that languages were expected to change and devs were supposed to "level up" as part of their job description. TW had the policy that "technical decisions are made by technical people" and I wouldn't be surprised if DRW had something similiar. What mix of languages should be used on a project should (imo) be made by developers who work on that code base. If Jay insists on working in a language he knows (from experience, he is a great Java dev) to be better, then more power to him.