Let's start with what I tweeted:

I don't think Mozilla understands how angry plenty of people are going to be when Firefox 57 is released and breaks many of their addons.

If you follow Firefox news, you already know what this is about; Firefox 57 is when Mozilla is going to turn off all old extensions, ones that are not WebExtensions (this is apparently different from being ready for Firefox Electrolysis, although all WebExtensions are okay with Electrolysis, or maybe there is something confusing going on).

Firefox Nightly builds recently switched over to disabling old extensions. Nominally this is just flipping the extensions.legacy.enabled preference from true to false and so I could flip it back, as I expected earlier this year. In practice all of my extensions immediately fell over, along with Nightly itself (it now hangs on startup if old extensions are enabled). Even the extensions that I thought were ready don't work now. Nightly is as Nightly does, and it was kind of broken for me in various ways even before this, but I consider this a pretty bad omen in general for the state of WebExtensions. According to Mozilla's release calendar we are less than three months away from the release of Firefox 57, and nothing works. Nor was there any sort of attempt at a graceful transition when I fired up the first version of Nightly with legacy addons turned off. I don't think I even got a warning.

(I don't know if this is because Firefox has no support for a graceful transition or because there are no WebExtensions versions of any of my addons, not even, say, NoScript, but neither option is a good sign.)

I'm pretty sure that Firefox has a great many current users who pay absolutely no attention to Firefox stuff due to complete lack of interest. These people are not up on news about WebExtensions and other such things, so they don't know about this change coming in Firefox 57. A certain number of these people use extensions extensively enough to create a new browser. As far as I can tell, these people are going to fire up their auto-updating Firefox install some time after November 13th and experience what is to them a completely different and much more stripped-down browser with what seems to be very little warning.

(Fedora is on Firefox 55 right now, and several of the extensions I have enabled in my testing Firefox aren't even Electrolysis compatible, much less are WebExtensions. I'm getting no warning nags about this on browser startup or any other time. Perhaps this is different on other platforms, but I suspect not.)

When these users get their browser yanked out from underneath them, they are going to be angry. And rightfully so; yanking people's browser out from underneath them is an extremely rude thing to do. Based on their behavior so far, I don't think Mozilla really gets this. The other interpretation is that Mozilla doesn't care if some number of people wind up angry, which I think is also a bad mistake. Mozilla seems to be so intent on going full speed ahead to WebExtensions and damn the torpedoes that they're ignoring a violent derailment coming up ahead of them.

By the way, one of the problems here is that the Firefox version of the WebExtensions API is incomplete in that any number of current extensions can't be (fully) implemented in it. You can track some of the depressing state of affairs by looking at arewewebextensionsyet. Remember, we're theoretically less than three months away from permanently turning off many of these extensions in their current state.