For me, FI means having FU money, and FU money means a level of freedom and confidence such that I never had to put up with toxic or unfair crap at work again.
Having FU money means I was more honest with my bosses when they asked the team tough questions -- and afterwards, teammates privately thanked me for articulating what they were scared to say out loud.
It means when some idiot started disrespecting and hassling me at work, and their management did nothing to fix the situation, I could quit.
It means more confidence to speak truth to power, which, ironically, leads to being respected more in the workplace, not less.
And it means (well, meant) genuinely enjoying my job more, because I wasn't stressing out about money.
So, yeah, pretty huge difference for me.