TL;DR: probably among my favourites in the action-JRPG genre, just for how consistently good everything is. None of the systems in isolation are "the best I've ever seen", but for a 35+ hour game, it's nice when everything is smooth and enjoyable.
For context, I have played a decent handful of JRPGs, with my favourites being probably Skies of Arcadia Legends, and Tales of Symphonia. In the Tales series, I've played Symphonia, Symphonia 2, Graces f, (never finished) Phantasia, and (never finished) Vesperia.
Story
The game begins by letting you choose which of 2 protagonists to follow. The game's story is broadly the same, regardless who you choose, but certain scenes are seen from different perspectives, and certain moments are missed if your chosen character is absent. I have opted not to replay with the other character at this time, but the game is good enough that I would if I had more time. I chose the female lead, Milla.
The story itself is...fine. The setup is pretty good, with Milla being an literal avatar of the world's god, whose powers are stripped by an unknown dark force early on. The story then shifts to a fish-out-of-water story for Milla, and a quest to regain her powers and destroy the dark forces. She is joined by Jude (the other - male - protagonist), who initially has no quest, but does want to be helpful to those in trouble.
This brings us to a major highlight of the game - the characters themselves. The story feels more like background dressing for the cast to play off one another in. The skits - a Tales staple - are here, and they are predominantly well-written and performed. And the cast is wholly likeable, and have decent arcs throughout - though there are a couple of head-scratching moments regarding character motivation. I was fond of basically every character by the end, even in the extended cast and bad-guys.
One sticking point I should mention though is, because there are scenes absent from certain protagonist play-throughs, be prepared for a couple of deus ex machina moments, where ostensibly the other protagonist has been busy in the background, but you will not know exactly how or why certain story beats happen unless you replay the other story. It's made doubly-weird where, despite having the skit system for optional additional dialogue, the POV character is never made aware of what happened during certain background story moments. From what I have read online, it seems that the better way to play story-pacing-wise, is to do Jude's story first, then Milla.
Specific examples, spoilers for some major story beats
In particular, when Muzet is introduced in the Milla storyline, she joins the party in barely 3 sentences explaining who she is and why she's there, despite being a "very important character". There's also a scene near the end of the game where Milla is separated from the group for a time, then teleported directly into a battle with a previously unseen "very important person" in a "magically alternate dimension" and no one explains how or why the rest of the party got there - nor that they killed off a couple other "very important bad guys" in the interim. It's...weird narratively, though excusable thematically as Milla is a very "go-with-the-flow" character, so YMMV.
Gameplay
The combat is fun and really well balanced. The difficulty curve was almost perfect the entire game. I did a little bit of grinding every now and again, but honestly, every time I did, it made the next boss quite easy. I like the "partner system", which allows 2 characters in battle to buff each other, and I liked how your MP is refilled just by doing normal attacks, which meant I never really ran out of magic - this is particularly nice, as the healers are also more-or-less always healing and being useful. The party AI is also pretty good, especially if you spend a moment to fiddle with the strategy and auto-item settings.
There is a very extensive level-up system, split across a skill-tree and buff-pool. I...can't speak much on it, as there is also an auto-level button, which auto-applies nodes on the skill tree, and I used that almost exclusively. However, it's there if you wanted some good character building options. The shop system is also pretty good, and made it perpetually feel like I was accomplishing things and getting stronger.
There are a smattering of side-quests per town. Some were bog-standard "kill this thing, get this item", but there were also several that were self-contained stories and world-building. There isn't a quest marker, so some quests did require me to look up where to go, but I don't consider that a bad thing - more an "I'm impatient"-thing.
Probably more that I forgot to cover, but this is getting long for a first "patient gamer" review, so I'll stop here. This game and Tales of Symphonia are now in contention for my favourite Tales game, so make of that what you will.