For me the main point is WebAssembly. Javascript was the only option for the web (As the article notices you can compile/transpile to Javascript but this was adding more complexity for less gain). With more options developers will use languages that better adapt their taste and needs. C++ can be highly optimized when creating WebAssembly code, C# and Java offer flexibility, Python and Groovy are easier to star to use, etc.

Javascript was used beyond it's own merits as a language. It was the only feasible door to pluguinless development in the web. WebAssembly will allow people to choose. And even that a lot of developer will still have Javascript as a first option, others will not, and the web development environment is going to deeply change.