You're speaking as if Rails is useless now, when in reality it's still a great tool depending on the job, especially since Rails has an API-only mode that works great with the modern SPA front-end ecosystem (sidenote: not every app needs to be a SPA). I built a company with it that provides a developer API, and that has a modern SPA front-end. Rails is still useful, especially for startups.

(And DHH didn't literally retire--he runs his company, Basecamp, which is built on Rails, which he actively maintains.)