Github, Shopify, Airbnb, Hulu and more are built in Rails, so clearly it does scale. You can do microservices with Ruby/Python as well. Ditto serverless. And my own company does this.

But comparing Rails (a framework for complete web dev functionality) to entirely different paradigms and use cases seems kind of silly. These frameworks don’t solve everything, but they make it far easier and cheaper to develop a website with under, say, 500 million users. Once you get that large you can start exploring paying more devs for better efficiency.