Academics are not, and don't need to be, good software engineers, because the tools and skills one person needs to build a proof-of-concept are different from the skills a large team needs to build production code.

Functional code and immutable data are fundamental ideas for managing complexity in big systems, irrespective of language. Even modern C++ tries to be functional until it has a good reason not to be.

(I also went to MIT, and I work on low-level systems at Google.)