Maybe calling these "breakthroughs" is a stretch, but anyway... Swift. I think that this is the best general purpose language ever created. By "best" I mean th

Maybe calling these "breakthroughs" is a stretch, but anyway... Swift. I think that this is the best general purpose language ever created. By "best" I mean that it has the highest productivity (which is determined by readability, static safety, expressiveness, etc.) after normalizing for factors outside of the language spec, e.g. tooling, libraries, compilation and runtime speed. React and Svelte. The first breakthrough was React, the second generation is Svelte and similar frameworks. Async / await. This is a major improvement to the readibility and mental model simplicity of the most common type of concurrency code.