And it was great! More importantly it was already a more or less finished product. The updates were slow, sparse in time and didn't change much (it took 3 years to get from v. 1 to v. 3).
Then something changed in 2011 and updates started showering almost every week for no apparent reason. It was annoying and I've completly stopped installing updates after v. 13(everything worked perfectly anyway). Then after 4 or 5 years I started to have a problem with playing youtube and twitch videos, so I decided to finally update my FF. It was already v. 57 (Quantum) and it made me absolutely livid. 2/3 of my extensions weren't working (and still aren't) and the ability to change UI theme was completely gone (and so I am now stuck with that bland default theme). And all that for no visible benefit on my part whatsoever.
I've immediately installed Chrome, Opera and Safari to see if they were any better, but ... they all are almost identical to the new Firefox (although I am now using Opera on mobile). There is almost no incentive to change from one browser to another now.
Well, it's year 2021 now, but somehow my user experience is worse than it was fifteen years ago. How is that possible I do not know.