Without going full-on with a Rails API backend, and pure React/VueJS frontend, there's still some options to add interactivity and responsiveness to the frontend when moving on from jQuery.
- stimulusjs is a BaseCamp extraction, doesn't do any rendering, just exists to provide some really straightforward interaction. Plays well with asset pipeline & turbolinks.
- react-rails also works with asset pipeline/webpacker, and gives you a straightforward way to render react components from your views. Works best with smaller components.