What Mozilla/Firefox needs to understand is that end users do not care about standards purity/principles. If core functionality doesn't work in your browser, people simply aren't going to use it. This is why the web is increasingly broken on Firefox--nowadays, about 10% of the sites I visit are simply utterly broken or slow on Firefox but work fine on Chrome.
Hell, even the $LARGE_CORPORATION I work at has all its developer tooling (including documentation, custom extensions, etc.) on Chrome. I've reported countless Firefox-specific issues, often due to missing API support, because no one internally tests on anything other than Chrome. You have to meet your users where they are.