Well, FIRE is about retiring before you're old. But really this is an idea for people with insanely high salaries that you commonly see in the US. It's for when you're earning several multiples more than you need to "be happy". All it's really saying is if you resist lifestyle inflation and the hedonic treadmill you can still be happy your whole life but be financially independent much earlier. It's not really about people earning close to median and living in poverty their whole life so they can retire.