Backend (and frontend!) can be use stable technology choices if you want to. There are also plenty of bleeding edge libraries/frameworks/languages that come out every week.
As an example, how do you want to deploy your backend? VPS, severless, Kubernetes? What database? Which language? Which libraries?
There are boring stable answers to the above for backend, just like there are boring stable answers to frontend.
Really, I think you’ve just found those boring stable options for the backend and you haven’t done that for the frontend yet.
React has been out for more than a decade and it’s the dominant way of building UIs. And there are pros and cons to this with 1000 solutions, but, really, plain React will work for most things you want to do.