Example:

https://xlii.space/eng/from-rust-to-ruby/

The thesis that you're making is biased. Huge tech corps can move away from Rails, but it's similar to argument of "why the most successful people in the world don't drive Toyotas". Which is true, but it doesn't mean people should stop using Toyotas and buy Koenigsegg instead.

Typed languages have consequences. Some designs are either non-ergonomic or impossible. Rust: if you want to have a swappable adapter you're in Box<dyn> world. Many apps don't have to live in Box<dyn> at all but they need to test which is the sole reason to change architecture and wrap in boilerplate.

None of these reasons matter if you're multimillion tech corporation with unlimited resources.

But these are very important reasons to consider when you have small-medium sized team and cannot afford to fight language.