I quite liked it, but I was always aware that I was watching a children's film and it's not reaching a level that would have you recommending it to adults. It's not a Pixar classic or anywhere near that, but it's not going batshit crazy either. I'm sure it entertained its target audience, though.
It's actually two films: (a) a six-minute CGI short, and (b) a 65-minute feature film with animation just like its parent TV series. They were released to cinemas on 29 October, so if you want to watch everything in order, they go between ep.38 and ep39.
1. Cure Miracle & Mofurun's Magic Lesson (6 min.)
This is pretty silly, which is good because silly magic is funny. It also has a chibbified CGI version of Mirai in a CGI world that owes a slight debt to Aardman Animations. (Look at the bees' mouths.)
It starts by telling us how to use the Miracle Lights that have been given to all the children in the cinema. You turn it on and wave it when the film tells you to. What you don't do is dazzle the person sitting next to you, bash them in the head and so on. Gotcha. Important safety lesson. Later we'll discover that these Miracle Lights will save your life with balloons if you're ever falling from the sky.
2. The Miraculous Transformation! Cure Mofurun! (65 min.)
The Magical World is having a 100-yearly festival. It's got towns inside balloons. There's a competition to get your wish granted, which is won by Mirai's teddy bear Mofurun.
Then... ENTER THE VILLAIN! It's a giant grumpy bear, as is right and proper for a Mofurun-centric movie. It's also strong, shrugging off the attacks of all three PreCures. (Since a PreCure can punch a lorry over a building, this is impressive.) Later we visit a land of bears who can only say one word ("bear"), plus an intelligent but slightly unfriendly little black bear who intimidates the others.
The only element that deviated from formula was the bad breath, which amused me. (There's a fruit with a seed that absolutely mustn't bite. If you do, you'll blast out a yellow gas cloud as if this were a WWI battlefield.) Apart from that, though, it's what you're expecting. The villain's really just lonely. There's a "death", i.e. a "wave your Miracle Lights" opportunity. (Spoiler: no one dies permanently in movies like this.) Mofurun gets transformed into another PreCure, which is fun, but this would have been less surprising if it hadn't been trailered busily in the TV series and mentioned in the film's title.
It's quite well done, I think, although the TV series would have done this plot in a standard 25-minute episode without blinking. It's empathic. The villain's story feels so inevitable that it would have been a twist have it been anything else, but he's still by far the most sympathetic, human villain (bar Yamou) in Maho Girls PreCure!. This is the kind of thing you'd approve of if your young daughter was watching it, but you probably wouldn't sit down and join her.