Firefox stands for the web of open standards: it’s good that the browser exists. However, it is slipping into insignificance.
A healthy browser ecosystem needs diversity so that one day one company cannot dictate to everyone how they should use the internet. We’ve been through this before, and it didn’t go well. On that note: Happy birthday, Firefox, may you have many more birthdays!
IIRC I downloaded Firefox 1.0.4 way back in the day, and kept using it until somewhere around version 6 or 7. Moved away when they started copying Chrome on everything. Rapid-release inflation was the last straw.