My professor, Dave Mason, Chair of Computer Science at Toronto Metropolitan University, only programs in Rust and Smalltalk, no other programming languages. Here's why...

Rust and Smalltalk are perfectly complementary languages. One is great when you need high reliability and performance. The other is great when you need dynamic flexibility and high productivity — this means perfect for prototyping and refactoring.

There are applications where I would prefer Rust for sure. For all others, I would choose Smalltalk. Smalltalk is unbelievably versatile and productive. In fact, a 2017 study by Capers Jones, the world's leading expert in software metrics, showed that Smalltalk was much more productive than, say, JavaScript, C++, Go, Java, Python, and even Ruby!

Dave and I were involved in this: https://levelup.gitconnected.com/mmxxii-year-long-celebrations-for-smalltalk-bed82541b7db.