I don't get this mindset. I'd much rather have the new guy spend a few months getting used to a new language, than have an organization where everyone uses different languages. It's a nightmare a few years down the road when you have 20 different projects in 15 different languages and the people who built them are mostly gone.
People are way too lenient with this stuff IMO. The goal of an organization should be to have one solution to each problem. For example we use .NET for backend and React for frontend. You don't need anything else. People love to talk about the right tool for the job, it's all BS. You can make pretty much any kind of website using react and pretty much any kind of backend using C#. The only reason to choose anything else is preference.
And sure maybe you have some data science people who need python, thats fine. Just don't have one guy using Py, another using R and yet others using Matlab. That's just asking for trouble. Pick one, stick to it. If you're going to make a change then migrate everything. If it's not worth that then the new tool probably isn't such a big deal after all.