> I'm curious about real world examples where a change has lead to a significant positive outcome in performance, code quality/maintainability, etc.

Another example: same language, new framework: In a Python web app, we needed to have websockets. But at that time Django had no real websocket support. But there is future proof framework that does: aiohttp! Also one might argue that you can use old django with websocket using another process. But it leads to a more complicated architecture. We want to keep monolith the app as long as possible/sane.