Re: Firefox's global market share dwindles ...
A lot of it is nonsense, and that bit which isn't doesn't add up to Mozilla "had to" break the addons as much as "it was easier for us that way."
Firefox 56 was the last non-Quantum version, and its security-updated brother, Waterfox, still rivals the current Firefox in speed, just as it did when Quantum arrived. It's single percent digits slower on any benchmark you can find. When is all this alleged speed from amputating the defining feature of Firefox going to arrive? It's been promised, but it's still not here.
Contrary to what you'd think reading the HTG article, FF56/WF does multiprocess quite well even with the legacy addons. I'm using Waterfox with e10s enabled now, as I have been for a few years, and it works fine, even with more than a dozen legacy addons.
Even if there are more addons for Chrome, they can't do what the old ones can for Firefox... not even close. Who cares if you have ten times as many addons that collectively can't even come close to what the smaller number of much more powerful addons can do in Firefox?
If people blame Firefox for addons failing to be updated to keep working, that's nothing new. PEBCAK, or however you want to refer to it. You can't code around user ignorance if you actually want the software to do something useful. "We're gonna be blamed if addon makers don't keep up and they get broken one by one" is not a valid reason to throw the whole addon subsystem away. "So, let's break them all and be blamed for that instead, only now those blaming us will be right."
The thing about making sure the APIs work and not worrying about addons specifically still fits even if you're talking about XUL addons. If having a powerful addon API means the addons have to keep changing, so be it. It's an acceptable trade-off. Those in active development will continue to make the necessary changes, as they have for the past decade and a half. The heavy lifters I'm using now in Waterfox are still being updated now, even though they're ten versions of Firefox past their supposed EOL.
"Developers had time to switch to the new API" is a red herring. They had the time, but very often, time was not what was needed. A more powerful API than what they were being offered was what was needed, and it no longer exists. All the time in the world won't make Webextensions do what XUL was able to.
I have a very exacting view of what I want in a browser. None of the Chromium variations, including Vivaldi, Opera, Brave, or Chrome itself even come close. Firefox still comes closer than any of them, but I have little doubt that in time the devs will continue to slice off anything unique that distinguishes Firefox from Chrome, and there will be little reason to consider Firefox as opposed to, say, Ungoogled Chromium.
Even with my very firm view of what a browser has to be able to do to be fit for purpose, I never once failed to find an addon in legacy Firefox to do what I wanted. I've got it just as I require. Many (about half) of the ones I
can't won't live without do not and cannot ever exist for Chrome OR Firefox Quantum, so if there's an addon gap, it was one that was in Firefox's favor pre-quantum. It only takes one really good addon to do something... I don't care if I don't have thirty redundant addon choices that all do the same thing as my one Firefox addon can if the other half of my Firefox addons do things that can never be done, ever, in Chrome or the new Firefox.
Not only that, but it was never an either-or. It was not necessary to rip XUL addons out in order to put Webextensions in! Firefox 56 had Webextensions, just as Waterfox still does right alongside its legacy addons, and all of the changes that Mozilla has made to Webextensions since v56 that are not now in Waterfox (since they came in after the fork) would be in Firefox just as much if they'd left XUL addons intact. It's a false dichotomy to say that they had to cut off the legacy addons to get more compatibility with Chrome addons. FF 56 had both. Waterfox has both.
The real reason Mozilla cut off the old extensions, if not my glib answer to that question in the beginning of this post, was that for years Mozilla has pursued a bizarre strategy of trying to compete with Chrome by removing every single thing it has that made it better than Chrome. Firefox is not Chrome yet; it still has things that make it better in a lot of ways, but for how long? Mozilla seems to think that if Firefox is essentially identical to Chrome, the existing Chrome users will come over to Firefox because it's so familiar and... wait, why would these users expend the effort to migrate to something that offers them nothing different than the product they're already happy with? No matter how much FF is like Chrome, Chrome users that want exactly what Chrome has to offer, nothing more and nothing less, will still not have any reason to migrate, because the browser they use already fits them perfectly. Privacy? Clearly not an issue for most, but if it is, there are plenty of Chrome clones degoogled.
What else would a Chrome-clone Firefox have to offer the user to lure them to switch? Mozilla's is a strategy that has shed market share for years and years, and the Mozilla devs just keep redoubling their efforts to lop off even more features and mimic Chrome's horrendous UI more and more in the hope of luring those people for whom Chrome is already perfect. In the process, they've lost many of the Firefox faithful they did have, and they've done so willingly and openly. Surely it will work, though, once some critical mass of non-uniqueness is reached, right?