For me it's more nuanced, and I wish I saw more of it.

You make your prototype or fit your product with a rapid dev framework, Rails is pretty much built for that, it doesn't intend to scale beyond it (see Basecamp: they don't pile onto a monolith, they make fresh new versions).

One you get that product fit, your codebase should still be small enough to rebuild it quickly in a more stable language. Java, C#, Go, Rust, whatever... something that gives you better runtime guarantees without requiring bonkers amounts of language hacks so you can spend less time writing unit tests and stubs and mocks.