"the engineers are bored and they're rewriting perfectly-good codebases in Common Lisp and OCAML for funsies" Had this literally happen to me, but I was a low

"the engineers are bored and they're rewriting perfectly-good codebases in Common Lisp and OCAML for funsies" Had this literally happen to me, but I was a low level manager and this was happening in another team. One thing I've taken from it, at the time the feeling around Sr Management was that we needed to allow this or we would lose the engineers. They allowed it, and after the conversion, those engineers left to start their own company. The remaining engineers had to deal with undocumented OCaml code and keep it running and were resentful. I have seen this with React vs Vue, where an engineer not liking React, just did his code in Vue. 'We have to let him do this or he'll leave', but he left on his own accord. Lesson, stick up for your codebase, and if engineers don't like it, let them leave or make them leave. The other engineers on your team will like it, and some of them will become your new Sr Engineers.