This points to the disturbing truth of how incredibly complete Google's monopoly is: Even browsers not based on Chrome are strongly pushed to implement Chrome's platform changes anyways.
It's been known since around 2010 or 2011 that the full extension system was too powerful for effective maintenance of Gecko. Going through XPCOM for everything prevents effective optimization within the codebase, and generally ensures that the APIs have to become less ergonomic compared to modern C++ (or JS, for that matter). Furthermore, multiprocess content tabs was heavily delayed because turning it on would break practically every extension (since you could no longer have synchronous access to content).
Moving away from that was definitely the right approach for Mozilla, but the timetable and effort into bringing up a non-XUL/XPCOM-based extension mechanism definitely left something to be desired.
Pretty much as soon as they added multi processor support they had to start throttling background tabs anyway, same as chrome. It's not at all clear that going multi process was a win. And years after they change their are still a bunch of things extensions did that don't work anymore. I was never a huge fan of XUL or any non-native UI, but it did it's job for years and it's replacement doesn't.
And due to their follow google nature of monthly updates there's no stable version to fall back on.
link location bar extension: this cannot be replaced with a webextension as mozilla refused to add the necessary API
websocket monitor extension: this is being built into the dev tools, after 2 years and counting
tab groups / panorama: every single extension that tries to replace this is terribly broken, because the provided extension APIs don't really support this use case or are super racey
like the link location bar extension it's impossible to write an extension to replicate the old refresh/stop/go button in the url bar. You can have 3 buttons, but that's stupid.
And before I get crucified: there aren't any better browsers, so I'll be sticking with Firefox, but it sure isn't anywhere near as useful as it used to be.
> Perhaps it's your needs, not Firefox, that are incorrect.
Giving a list of my needs is pointless. Also, I never said that Firefox was incorrect. I said that it no longer meets my needs.
Mozilla has made a business decision to address a user demographic that I am not a part of. I don't have enough information to be able to say if that decision was correct or not. All it means is that I no longer use Firefox.
Firefox is faster and more secure now that they don't have to maintain compatibility with a bunch of old extensions that touch a bunch of internal stuff. Firefox's WebExtension API goes well beyond Chrome's at this point and is still adding features.
Mozilla's decision to remove XUL Extension support was directly a result of their decision to replace XUL in favor of HTML5 as the UI design language of choice.