If a browser has too many compatibility issues, users will switch away. Outreach to the sites in question takes time and is often unsuccessful. Quirks is the pragmatic answer.
My iOS/Safari is so bad, I have both Firefox and Chrome installed as a backup in case it doesn't work. They should start fixing Safari for real instead of adding Quirks.
I have bad news for you. On iOS, Firefox and Chrome use the same WebKit as Safari (because Apple doesn't allow third party browser engines on its App store).
