If that's the question... Let me assure you that there are decades-old pieces of code inside of, and used to assemble, many modern AAA games coming out of mature studios. The systems and tooling is typically carried forward. I don't think this is some big secret and you've intuited exactly the reason why:

> game dev tools are about what can get the best results quickest rather than any sort of technical specifics. It is a business after all.