I wouldn't call it a breakthrough as the ideas are not new, but I consider Rust to be a major practical advancement that brings ideas into the mainstream that w

I wouldn't call it a breakthrough as the ideas are not new, but I consider Rust to be a major practical advancement that brings ideas into the mainstream that were formerly just for "academic" languages. It's the first IMO viable alternative to C and C++ for systems programming ever, and its safety features represent a successful transfer of provable-safety ideas of academia into a practical language that people actually want to use for real stuff. As for true breakthroughs I'd say the last big one was modern deep learning.