I fail to understand why people call Firefox as broken. I exclusively use Firefox (with all the ad-blockers) and almost never have any issue in rendering a webpage or a need to switch to another browser.
If Firefox was broken broken all other browsers would be beyond broken IMO as none of the mainstream browsers really hold a candle to it for my workflows even today.
But compared to itself a few years ago the advantage over other browsers has diminished in every aspect I care about except maybe security.