I think it's quite the contrary. Rails integrated Webpack a long time ago in it's basic installation so if you do `rails new my_cool_app` you have Webpack ready(and preconfigured with React/Vue/Elm etc.) right out of the box. Also it moved away from Coffeescript and jQuery.
And for the full page reloads, which you think is weird, there are Turbolinks(again preconfigured in the basic install) since like 2012. I'm not sure React or other reactivity foos already existed at this time. And now we have things like Stimulus and Stimulus Reflex and others so the development ain't stoping now either.
So the feeling that Rails are stuck or out of date is really only a feeling.
And for the full page reloads, which you think is weird, there are Turbolinks(again preconfigured in the basic install) since like 2012. I'm not sure React or other reactivity foos already existed at this time. And now we have things like Stimulus and Stimulus Reflex and others so the development ain't stoping now either.
So the feeling that Rails are stuck or out of date is really only a feeling.