Decided I might as well post a comprehensive review here.

Combat:
Rebirth expands in small and large ways on the foundation created by Remake, and combat is fun throughout. Boss fights remain the highlight, but regular encounters in the open world or during story segments are also quite fun. They strike a good balance between the mechanics of abilities, spells, limits, summons, and synergy attacks. You always have a bunch of options and all the characters play differently in cool ways. Some are definitely 'better' than others, but by the endgame I was enjoying the specialties of every character, even Cait Sith. The game does reuse a couple of bosses a bit too much, with a couple of encounters happening 3 or so times, but aside from that, combat remained a thrill throughout.

Exploration:
The open world is best enjoyed in small batches. Doing too much of it in one moment I found to be too big a diversion from the strengths of the game's storytelling and linear setpiece moments. There are some good mysteries to discover out in the open world, though sometimes the exploration can feel tedious or repetitive. There are some segments of the game's story missions that focus on puzzles that maybe overstay their welcome just a bit, but not in a way that I felt too overbearing.

Minigames:
Genuinely can't believe so many people complain about these. To me the minigames are a huge part of what make this game so fantastic. It makes the world feel so real to be able to actual play these little games, and provides a nice distraction from other aspects of the game.

Story:
(spoiler free segment): The characters are even more fantastic than ever. Voice acting remains top notch throughout and combined with the animations, puts so much life to these characters. Their relationships and interactions feel so real and develop nicely over the course of the story. While being the second part of a previously developed story that has a conclusion yet to come does provide some stagnancy for certain characters, for the most part they all get a big moment to shine independently from the rest of the party. The biggest weakness to the story is probably that there are segments that feel a bit aimless. Certain chapters focus primarily on character interactions and worldbuilding, but it can be easy to lose sight of the bigger picture of what the characters are trying to accomplish, which often amounts to "follow these nameless entities around the world." This is largely due to how the original game was structured, so I can give it some grace, especially since usually these moments are filled with so much charm and fun that you don't necessarily care.

Spoiler-lite story review:
The last chapter of the game makes some pretty large departures from the previously established story. Most of these were at least somewhat expected by the way Remake ended and Rebirth opened, but even with that expectation, I do feel that they lacked a little restraint to execute these masterfully. The final boss encounters include a multiphase fight against the normal boss from this point in the original game, followed by a 5-phase fight against a new boss not in the original that feels a bit too long and repetitive from what came before. They don't do a very good job justifying why this fight needs to happen or what would happen in the story if our heroes lost, which is part of what causes the frustration. The game also diverts from some major expected story moments that make a deep impact on one character in the original, and this change does have me a bit worried about the places they'll go in the final installment, especially with his character development. Even so, I would say 11-12 of the 14 chapters in the game are nearly perfect, enough so that reflecting on these moments after the confusing endgame mostly causes that disappointment to wash away. I just hope they can stick the landing.