Earlier quoted context omitted.
> Web browsers are a terrible place to do innovations, a major problem being the absolute backwards compatibility they need to maintain. How so? The biggest innovations in the browser in recent years have been shadow-DOM type stuff like React/Vue, plus WASM and WebGL. None of these are backwards compatible with older browsers.
It's the web browsers which need to keep perfect backwards compatibility with essentially all existing web standards.
Like what? Sites don't ask me to allow ActiveX or check if I have Flash installed, and CSS support across browsers is not uniform even now. JQuery did more to ensure JS compatibility across browsers than the vendors themselves.