This game runs like shit even still, having just released the last part of their DLC. It's amazing how much effort they can put in to just barely getting to a working state. But it's not the devs fault or anything, they can't do anything about the worldwide campaign that follows the timely releases of the games, with plushies, toys, cards, you name it.
The game itself, hidden under a mountain of bullshit, is actually really good. I thoroughly enjoyed playing through this game when it came out and I loved all the characters and adaptive music, and new Pokemon.
The way the world is built allows you to choose where you want to go, ditching a linear approach to the badges, and adding more challenges in addition to the gyms. It's fun to go your own way and explore this big open world. It can be a little of a letdown when you come around to a gym and find that you're way overleveled, but it really isn't a big deal given the miraidon abilities sort of subtly guide you around the map to try to keep you from experiencing that kind of over leveling.
The battles are fun and a few challenged me, but I do miss the days of intense battling. Now you don't really have to worry about your HP because you'll probably just get healed by a random NPC after anything you do.
The elite four wasn't that much of a challenge to me and it was really disappointing that the arena was just some white-walled boring gymnasium. I miss the theatrics of some of the older games.
All being said, the online isn't that complex, but having it and having the ability to play co-op in the open world is really really cool. I just wish I had enough friends interested in adventuring with me.
Anyways, if you're willing to look past how awfully the game performs and sometimes looks, I think you'll find a decent game underneath.