It depends on what you mean by FF elements, right? To me Final Fantasy isn't Chocobos, Crystals, or specific magic, big swords, or any of that. (Note: I'm the type of person who'd sooner see FF16 take a big stride & be some sort of sci-fi thing by way of Mass Effect or Star Trek, or a steampunk thing by way of Blade Runner and Deus Ex, or be something crazy different entirely (I think FF could do a great spy thriller plot) than be wars over crystals or the will of the gods again.) Those are component parts that sometimes crop up, but I'm A-OK with them being entirely absent, to be honest. Eidolons, airships, they're cool elements - but I actually think FF would be better off - in games as well - if it took large thematic leaps outside of that stuff more often.
So, yes -- TSW jettisons a lot of that and a lot of those traditions, but what remains at the absolute thematic core of the story is basically the embodiment of what Sakaguchi's Final Fantasy was often in pursuit of. TSW's themes are most similar to FF7, 9 and 6 - Sakaguchi's favourites in a story sense - the concept of two planes colliding, of a living planet, of the life force of the dead returning to the planet (and being blocked by a malicious entity) - even the ending where the trapped spirits are freed and sort of float away is (very deliberately, they've said) analogous to a science fiction version of The Sending.
Much of it is ripped directly from FF7, though a lot of people don't realize it - the 'ghosts' in TSW are a more literal (and antagonistic) representation of the forces of the Lifestream that make up Holy at the end of FF7, and the film's ruined New York City setting was actually built, initially, out of early FF7 concept art. FF7 was originally set in a future dystopic Blade Runner-esque NYC with an upper city and an under-city (present in TSW), but that became Midgar when another little upcoming game, Parasite Eve, was also set in New York - if not for PE FF7 could've been set on (an alternate version of) our planet, incredibly. Things like the Hardy Daytona are almost a hang-up from that period, when FF7 was, for a brief time, like FF15 in its 'ripped from the real world' style. The protagonist, Aki, was named for Sakaguchi's mother, who died during FF7's production and supposedly caused a major shift in that game to prompt thought about the nature of death & life force. It still has its obvious nods, too; the Chocobo cameo, the Cid character (Present as Sid) with an airship (The Black Boa, which is very reminiscent of FF8's Ragnarok), yadda yadda. It has its smaller nods, but it's more FF in theme than in specific surface-level substance.
So is it FF? Yes, absolutely. I'm one of those people who thinks FF's greatest strength is in how broad it's been (despite 9, the reverent one, being my favourite) and the entries in the series that I respect the most really are the ones that throw huge swathes of it into the trash and just run with their own stuff (FF8, born out of the same brave era as TSW, is similar - it has so little in common with the rest of the series in truth - almost half of its summons are new and mostly never seen again, there's no bloody crystals, everything's mega alien compared to everything that came before. I love it). But it's still absolutely FF, and I think that about TSW too. I have a great deal of respect for the movie's themes and ideas, even if they aren't well expressed - and those ideas are absolutely, undeniably FF to me.
On quality:
Is it underrated? Sure. Is it a gem? A great movie? Even a particularly
good one? No. The dialogue is clichéd and the story, which starts out on some very interesting ground indeed, gives way to nonsense, then a paint-by-numbers back half that really is incredibly uninspired. All that stuff would've got it heavily criticised if it were a standard live-action Hollywood movie as well, but even with those problems TSW is a pretty standard mind-numbing Summer Popcorn flick. It's not terrible, but the story is uninspired (strike one), it's a videogame adaptation (strike two) and the technology just wasn't
quite there and it creeped a lot of people out, though it was a technical achievement (the third, and most fatal strike - plenty of basic action movies with worse dialogue/story than TSW gross millions).
The prime difference is that I just think AC is standard-issue anime guff, doesn't do anything interesting with one of gaming's strongest and most iconic casts, and actually, in several instances, diminishes FF7. TSW is at least reaching for more, but it never makes it. AC is far better at being what it is, but what it is... is uninspired, to me, anyway. The fights are pretty but I don't feel anything because I'm not invested in any of it because the story is paper thin and arguably nonsensical and the dialogue is genuinely painfully awful.
It reminds me of the Star Wars Prequels, actually. I love Obi Wan, one of science fiction's finest, just as I love Tifa & Cloud - but I feel fuck all when I watch him fight Count Dooku or Tifa whatever that guy's name was (Loz?) for precisely the same reasons. There's no stakes, no emotion, no nothing. (AC's fights also have a really poor sense of space/location apart from the Cloud/Yazoo(?) one towards the end, which is a massive problem - the Ancients City one being the worst offender.) It's just pretty. For me, AC may as well just be another bloody
Dead Fantasy. (RIP, Monty.) This is just why I don't think AC is very good, basically. I also realize that I'm a bit of a cinema nerd and so probably am holding it to a higher standard - and I also think FF7's ending was magnificent and they were foolish to ever touch it. But I get that a lot of the fanbase wanted more closure than the magnificently open-ended ending offered and that many of them aren't as bothered about crap like cinematography.
Even now, TSW's Rotton Tomatoes rating pegs it at 49% - Advent Children's sits at 33%. They're both bad movies, TSW is just IMO the better of the two.
On Legacy:
As for TSW's legacy, it
is enormous, absolutely. It should be enormous to anybody on this forum anyway, as it had an astronomical effect on the way Square made games thanks to the tech/pipeline developments made in its production (and the fact it led to Visual Works), but beyond that TSW is still massively remembered. Disney, for instance, head-hunted about 20 of the top people from TSW and hired them away from the various companies they'd scattered to at great cost and put them on Tron Legacy (mostly on the young Boxleitner/Bridges stuff) because they were considered the real pioneers of 'realistic' CG animation. TSW is I think as seminal as Toy Story or The Matrix in terms of how other studios sat up, took notice, and used what it did well with CG in other ways in other movies - just the difference is it wasn't successful. It's a fairly large case study in many animation degrees and stuff now.
From Nobuo Uematsu, explaining why he left Square:
"[Square Enix CEO and president Yoichi] Wada took a couple of locations to a fortune teller named Pao," said Uematsu. "Pao said the Meguro space was not going to bring any fortune to the company, and pointed to Shinjuku. That's why he decided to move it there. I heard this directly from Wada."
http://gamevideos.1up.com/video/id/17537 7 minutes in.
