What is in this particular case that requires outdated tools? If they are code, certainly you can write them on VS Code or whatever you likes, and only need to compile and load on the original tools, can’t you?

It’s more the library and language side. Typically you are years behind and once a version has proven to be working, the reluctance to upgrade is high. It’s getting really interesting with the rise of package managers and small packages. Validating all of them is a ton of effort. It was easier with larger frameworks

You need tracability from requirements down to lines of code. It's a very painstaking process.