I think what the OP meant by 'modern,' was an equivalent of Rails that uses the technologies demanded by the tech industry today. On the one hand, the industry went to Python because a ton of data science libraries were written in that. On the other hand, React ended up real dominant on the front-end because of all the sh*t code people put between HTML JavaScript tags. Another route, is any promising asynchronous and scalability like Node or Elixir. So these divergent vectors make something like a Rails that can serve the needs of big data, snappy UI and scaling while at the same time using the team we've got super difficult. The needs of the industry have created an oblivion of the solution that was always already there, Rails.