This movie isn't emotional, it's not entertaining, and it's just not very fun either. Not to be too cruel, but this may be the worst Pokémon movie that I have ever seen, even worse than the Hoopa movie.
For one, the plot is way too straightforward. The Pokémon Keldeo wants to defeat Kyurem (a supposedly evil Pokémon that has done literally nothing wrong towards Keldeo) to prove to his mentors that he's strong. Anyway, Keldeo loses to Kyurem and ends up getting his mentors frozen, so Keldeo runs off and meets up with Ash and his friends (the main characters), thus leading to an 'epic adventure.' Just kidding, it's actually quite boring.
The pacing was quite slow, yet frantic at the same time. The whole movie just involves the main characters running, stopping, running, and stopping, with little room to breathe or hear any of the characters personalities, and the action isn't exciting enough to keep you interested. The voice acting in this movie is dreadful, either the characters are too whiny (like ash and his companion Iris), or don't even put any effort into their lines, like Kyurem. He sounds like an old, grumpy man who got out of bed at the wrong time, so you can't even take the main villain seriously. This is some of the most basic dialogue in a movie, that I have ever heard. None of the characters have any charm or personality, they're just reading a script without adding any oomph, except maybe Ash and a single line from his friend Iris about doors.
"Now aboxcat," you may be asking, "are there any redeeming factors to this movie you whiny little baby?" Well, I guess Keldeo's motivation to becoming as strong as his mentors is a tad bit intriguing, but you don't get enough time to see what they were like in order to become invested.
You won't gain much from watching this movie, trust me, just go watch Detective Pikachu, a way more entertaining experience.