Its great to see they are going to drive firefox off a cliff with yet another anti-user decision.
The situation with popular extensions has improved, but there is going to be a lot of pain, especially with XUL functionality that they refuse to implement in WebExtensions.
The question is how much the extensions can do, in the old model they could do anything firefox code could do, in WebExtensions model, they can do only very limited set of things.
On one hand it is quite sad to see firefox extensions go, on the other hand the old model was a maintenance hell both for firefox developers and for addon developers, because smallest changes in firefox ui were breaking bunch of addons, and even changes in addons themselves were breaking other addons, which all had incompatibilities and had to do lots of subtle hacks to work together.
I have worked on firefox addons for several years, and had to quit firefox when they started ignoring addons and investing in old addon sdk. But saying Mozilla is intentionally killing firefox is not fair the whole thing was shaky and full of hacks and would crumble by itself too.
What they should do now, is splitting their ui from the engine, so that advanced users can hack on the ui and get all the benefits of old addon system without the mess. If they fail to do that brave browser with https://github.com/brave/muon will take that niche.
And no, it's certainly not just an administrative deadline. For now, you can still tell Firefox Nightly to install legacy extensions, the vast majority of them are just by now completely broken, because Mozilla is ripping out all of that legacy code and refactoring what's left.
Here's a list of all of the things that they can get rid of: https://bugzilla.mozilla.org/show_bug.cgi?id=1347507
It's true it's still there, but I think the plan is using it less and less. No new UIs are written in it and many things have been rewritten from XUL to HTML5. Eventually it could be removed entirely.
Its amusing to me that mozilla expects everyone else to be moved off XUL, but not their own code because it has legitimate reasons....
Hilariously, dispite the pro-privacy stance mozilla pretends at, they want to start tracking urls visited
Why keep using firefox? Because I love Mozilla so much when they clearly have zero interest in my needs as a user?