A Rails project I'm working on has this LOC

  Ruby 12169
  ERB   2339
  Vue  24895
  Js    4526

The Vue frontend is indeed more complex than the Rails backend, and in my experience Vue is much simpler than React. My customer organized the Rails app with models, controllers, api/v1/controllers, jobs, services (naming only the most important stuff). It's not bad to work with.