The best time to switch to Firefox was many years ago. The second best time is now.
I stopped liking it some time around v2. Maybe late 1.x series, don’t remember.
I left over a decade ago.
Still bloated with a bad UI and offering little I can’t get in almost any other browser, all of which qualities are sharply contrary to the ones that made me start using it in the first place. They’ve changed none of what made me stop liking it.