Who is this "we" you talk of?

We did?

Who is this "we"? I still use it, never stopped.

When? There have been a few times people stopped using Firefox in large numbers.

One of them was when Chrome first came out. Firefox (and every other browser) at the time ran every site in one process. As sites became more reliant on Javascript, which was usually poorly written, that meant any one tab having a problem made other sites and even the browser's own UI unresponsive, or sometimes crashed the whole browser. Chrome's multiprocess model was a revelation. Firefox didn't get its own implementation until 2016.

Recently, there's been some movement away from Firefox due to Mozilla making decisions people don't feel align with open source, the open web, and privacy. The one that has me looking at forks is the planned addition of terms of use to the browser. Terms of use are for an ongoing relationship between a service operator and a user; Firefox is local software I'm operating myself on a computer I own. Its fine for optional online services like Sync to have terms of use, but the browser should work without those.

Misinformation

Firefox is essential for its various forks even if you have gripes with it

I never stopped using it. There are privacy issues with all browsers. I like how Firefox works, but I regularly end up using Firefox, chrome, and edge all at the same time. I use them for some compartmentalization of my tasks and work lol

I stopped using Firefox for four core reasons:

Their investment into AI How they submit and work with their Google overlords to some degree Their browser putting in more and more unnecessary and unasked features (like Firefox account for one) Their Terms of Service

The thing is, I never have. Chrome is absolute hot garbage and spyware, all the Chromium forks are all flawed and bugged and still feed into Google's dominance because of engine and stupid Manifest bullshit. Firefox, despite all the stupid things Mozilla did and still does just works the best and is not Chromium.

Firefox is better than most but still smugly makes anti-user changes which are complete dog shit.

Remember when they turned off your ability to choose to load extensions that weren’t signed, because fuck you?

Fuck Pepperidge farm, I remember that shit.

Or how about DNS over https, because fuck you, user, why should you have any say over name resolution when you might use that power to block ads and malware?

I've been back to Firefox for about a year now. Left chrome for it.

I never fully did, but I did end up using Chromium more than I wanted to:

1. Some poorly written sites refuse to work with FF. My water company, for example. They eventually fixed it after I complained multiple times. Now they display a warning that it's "Optimized for Chrome" but no longer flat out prevent FF from logging in (you know, to pay bills and such).
2. FF Desktop still doesn't support PWAs, and their recent update says they're working on it, but they're half-assing it (installed web apps will still have the menu bars, address, bar etc). I self-host a lot of web applications and want them to appear like native apps. Hence, Chromium.
3. There was some recent ToS / Privacy Policy change, and everyone was knee-jerking "time to abandon Firefox" as if there's anywhere better to go. (This is probably what you're thinking of)
4. A good while back, Chrom(ium) was just flat-out faster. That's been a while, and I think when FF's "Quantum" update (or whatever it was called) came out in like 2016 or 2017, it put it back on par.

Still using it here

I don't even remember many times Firefox/Mozilla has changed its extension API and broken everyone's add-ons. It gets tiresome.

I am lazy and have yet to switch to a new fork.

I recently tried to migrate to Firefox after the v2 extension changes in Chrome. I worked, but there were a few things that bothered me.

Chrome and chromium browsers will automatically use the window last used in the MacOS workspace you are in, and this usually works nicely when you have a work workspace and a personal workspace. It keeps things nicely separated when you click on links. Firefox doesn’t do that. It uses whatever window you last accessed. Not the end of the world.

The real problem I had is that the performance when using web tools like grafana in Firefox is so much worse compared to chromium based browsers. It was unbearable. I haven’t tried WebKit yet to see the same services in safari, for example.

I believe you're thinking of a ToS change where the wording was incredibly vague, leading to some outlets to claim they were selling browsing data to 3rd parties and AI modelers. They changed it right after to specify that the data they were using wasn't browsing data, and the data they did gather wouldn't be used for AI. They are not as invasive as google, but you're subject to Google on Firefox because of the ubiquity of their telemetry and search optimizations across websites. Firefox with an add-on such as noscript is much better than Chrome still, in my opinion. At the very least, it's nice to have a browser that doesn't work to undermine its own add-on functionalities.

I have a silly reason! I got a windows phone and loved it, so was happy to use Edge (when it was still its own thing and not effectively Chrome).

Edge's PDF viewer was great, and in general things were speedy, got out the way, and best of all it synced bookmarks to my phone. :) I also liked the rewards system for using bing, and between microsoft and google, I regarded google as worse ethically. (Obviously... yeah not a solid argument)

I think I switched back to firefox and variants mainly because I started caring about my data, open-source, and also those advantages Edge had were eroding in real-time, with adverts, nagging, and Windows things creeping in - the rewards ended, the chrome thing, it started feeling like the IE days again.

One of my coworkers uses it still, and it pains me to see what new AI gimmick is being shoehorned in.

If I stopped for dumb reasons, I like to think I came back wiser for it. :)

Because Librewolf exists and Mozilla became an adware vendor.

No, chrome came out and was that much better than every other browser at first.

Back in the early days Mozilla redesigned Firefox interface. It was so incomprehensively moronic that I moved to Chrome.