Earlier quoted context omitted.
Sorry, but that is just wrong, Certain types of APIs are infeasible to provide, because mozilla is too time and resource constrained to invest major resources into spec'ing, implementing and maintaining "niche" APIs. So far, Firefox did not even manage to reach chrome parity, let alone bug parity. If you look at the Advisory Group meeting notes (in charge of new APIs AFAIK), there is almost nothing still: https://doc…
> Sorry, but that is just wrong, Certain types of APIs are infeasible to provide, because mozilla is too time and resource constrained to invest major resources into spec'ing, implementing and maintaining "niche" APIs. I don't know how you come to this conclusion. They've been able to maintain XUL up until now and whatever they end up with in this new API, it'll be cheaper to maintain than the monstrosity that is XUL…
PS: As to maintaining XUL vs WebExtensions API, they always maintained XUL/XPCOM themselves because that's what Firefox itself uses, meaning the entirety of Firefox developers "maintains" that "API". They regularly broke stuff for add-on developers, which was sometimes annoying, sometimes avoidable, and other times just necessary.
Some add-on developers learned to adept to that, other add-on developers switched to the add-on SDK (which like WebExtensions is a limited API, just not chrome compatible) if it was feasible, and a lot of developers will switch to the WebExtensions API if feasible in the future or even now.