We talk about this like once a week, but here we go..
What I've noticed from people who hate it is that they simply didn't understand the story
This is a presumptuous assertion and feel the need to once again state my unrequested opinion.
I always say I'm not really a gamer as I've played only very few games that weren't FF. But FF I've played every single one of them, it's my obsession, my special interest, I talk about it to people in the street when they ask me if the train is late.
I love every single one of them, despite all the bs that comes with it, cause objectively the flaws in each of them are very easy to point out, they're far far far from perfect games. But what can I say, I love them. Some more some less but love them all.
The XIII trilogy is the only one I sincerely disliked though. The story isn't the worst thing ever conceived in humanity like Arte would have you believe, but I think it's bottom tier compared to many other chapters. Caius and Lumina are to me the only decent characters spawned from the three games and Lightning being a mix of Cloud and Batman doesn't help bring pathos to the story..but alas, some people like that type of hero.
I hate the gameplay.
Do I think these are bad games? No, they aren't, they're good games. Then why I hear you ask. Cause this isn't Final Fantasy. This isn't Final Fantasy.
p.s. I'll repeat it till I die but the Shivacycle was a capital offense too.