I started before it was called Firefox, and it was similar story.
I abandoned Firefox last year to the Chrome Opera, So i have been bitting my fingers for years, Firefox was slow, and I knew Chrome was better, and I had waited.
I used to force the usage of Firefox as the resident IT, with over 150 computer's default browser and later grew to 250. But every year since the introduction of Chrome, I have had more resistant, Chrome was faster, and better from those employees who knew IT, and may be 4 years ago, someone who is absolutely computer Illiterate came and asked if she could use this Google thing (Chrome). I asked for a reason, because I was curious how she knew, it turns out someone helped her using Chrome, and the speed was much better. She since then loved using it. And that wasn't only case, there were many other similar examples. And others from friends and family as well.
It was at that time I gave up.
Before then many within the Mozilla communities were begging for a better, more performant browser. That was right after Firefox 3, the goal of Firefox 4, the project of e10s. We thought JS was the problem, we advocated Spidermonkey being faster in benchmarks, but not much in UI or general feel of the Browser.
Mozilla then literally gave up making a better browser and its users, and went on to built Firefox OS. Their ideology of Javascript is the best, build an OS with JS. It was pure luck they had a small group of people crazy enough to work on Rust, and Servo as an experiment which later turned into what we had today, Quantum.
From the outside it was what i call a management and vision issue. And Mozilla left a very bad taste in my month. There used to be Article from Ars every month showing the decline of Firefox usage. I kept wondering at some point they should become worry as with less market share means less money from Search Engine, I dont think they see that as a problem until fairly recently.
It wasn't until a month ago, someone on HN posted an comment on Mozilla that helped me Grief. It was never their intention to have the best browsers, or to care for user experience, that wasn't their main Goal. Their goal, as it always has been, is an Open Web; all others are secondary and merely the results for their first goal. They weren't here to compete, they were merely here to make sure the Web is open.
It is good they are now back to Focus on Firefox. With WebRender, more Quantum parts, Firefox's future is bright. I am using Firefox now, but I wont be advocating for it any more, I guess everyone just choose what they want.
Sorry for a long rant, but that is the results of someone who has been following them since Netscape era.