To be clear, I am not suggesting the WASM canvas approach for ordinary web pages. WASM is for things that are unto themselves full-fledged applications, with the convenience of instant access to running them in a sandbox on any platform. The game described in the article certainly makes more sense with WASM than HTML5, as it uses web APIs for doing something that isn't displaying a standard web page but instead needs to conform to a specific set of characteristics to provide a consistent and polished user experience.

Also, while Unity doesn't, features like canvas copy-pasting can be implemented manually or by another framework. Non-English input works fine with WASM; if it doesn't render, it's because the application developer didn't include a font that supports those characters, since there's no fallback-font kind of thing going on. But this stuff is exactly the same as developing any kind of non-web application; if the framework doesn't provide a feature, you have to provide it yourself. It needs to be approached from an application development perspective rather than a web development perspective; you don't get the freebies of web, both the good and the bad, but this gives you much more control and capability.