It can be a 99.99% close-match, but if it doesn't include key methods like a runtime method_missing, then it's hard to see how we'd reimplement Rails and our code base on top of it.

I think people focus on the superficial similarity of Crystal, without thinking what semantics need to be the same for it to use usefully similar. And those semantics aren't there, so it doesn't matter if it sorts of looks the same and includes most methods.

I feel like if it was tractable to run Rails on Crystal then someone would have done that.