I didn't mean copy-paste reusability, I meant packaging code into reusable modules (e.g., NPM packages, Ruby gems). This has nothing to do with OO, really. But

I didn't mean copy-paste reusability, I meant packaging code into reusable modules (e.g., NPM packages, Ruby gems). This has nothing to do with OO, really. But I don't disagree with your point about immutability.