If you combine together all the static web 1.0 sites in the world with all the backend-as-a-service companies (Commercelayer, Stripe not exactly, the weather ones), and mix in the mostly-just-plumbing backends you can come up with by stitching together AWS offerings, and top it off with all the things you can do by writing less than 100 lines to run a Lambda function, you have covered a huge number of use cases without ever needing to learn Rails.