Dude, Django and Rails have basically improved in their tech while staying conceptually sound and approachable.
This is a cop-out. You pretty much have to relearn the JS environment every other year. It's a colossal waste of time that only junior people would be willing to tolerate for a marginal (if any) productivity gain.
Django's deprecation policy is practically the same as React's, except React provides codemods for every release, allowing you to automate code migrations.
And if you think Rails hasn't changed, you've probably not been using it long enough to remember the early drama. Not to mention Django's Python 2/3 conundrum (also class-based views). Heck, Django's development on top of Python's is aptly comparable to e.g. React's on top of ES.
So what? React is one library in the ginormous pile of tiny little dependencies that come with any JS project that's large enough, and those don't have the same policy and are subject to the incessant churn of the ecosystem.
I've been using pretty much the exact same packages for a 5-year-old Django project with no need to migrate needlessly.
I've had to migrate JS apps that were just one year old and tiny, and the amount of pain was far larger than upgrading a 50k LOC Django project.
This is a cop-out. You pretty much have to relearn the JS environment every other year. It's a colossal waste of time that only junior people would be willing to tolerate for a marginal (if any) productivity gain.