I'm reminded of the Smile PreCure movie. They're both perfectly decent, with a surprisingly strong emotional ending, but also a bit thin. It feels like a film by TV writers. This would have made a good episode. It might still, in fact, if you edited it down to 25 minutes. That probably wouldn't be hard. There's no attempt at the kind of complexity or depth you'd want from a movie, resulting in something that's less dense than even a PreCure TV episode.
In fairness, though, the film has clear themes and emotional weight. One early conversation is about Mana's mother's wedding dress, worn before her by Mana's late granny. This is light chit-chat, but it's also quietly introducing themes of death, loss, the passing of time and the value we give to old things. The dress is a bit worn. The lace is past its best. Similarly, four years ago, Mana's dog died.
These things will be crucial.
There's a non-villainous villain, Marsh. He grieves for forgotten things. He makes people's possessions fly out of their bedroom windows and make a flying garbage whale. This is cool. He's nice. When the PreCure get indignant and fight him, you'll be wondering why. Admittedly his animated dolls can be creepy and he'll soon be trapping people inside their memories, i.e. stealing their futures. However:
(a) that hasn't happened yet,
(b) that's attempted niceness too. Marsh is giving everyone their happiest memories, to protect them from future loss and bereavement. He means well. "You can forget everything painful and sad. You can smile forever."
In other words, Mana's about to get regressed to primary school age, to be with her granny and dog. The other girls get something similar. Cure Sword gets little emphasis than you'd expect, though, since the film could have gone to town with her on this. She has a tragic past, having lost her world and everyone she knew.
What happens after this is fairly predictable. Mana's approach is pleasingly sensible (trying to contact her friends), but soon she'll be unable to part from her granny and dog. (They're all memories, mind you. She hasn't time-travelled. Her loved ones are yet more of Marsh's dolls, which raises the slightly spooky question of who's speaking when granny has a heart-to-heart and gives advice that Marsh would have hated. A ghost, perhaps?)
There are cool bits, e.g. Davi paragliding off a building, or the fairies jumping into cinema screens. (I'd love to see those cutesy blob PreCure fairies portrayed as the dark faerie of myth. It won't happen, but it would be funny.) There's also blood. (Only a little, but no other PreCure movie has any at all.) However there's also occasionally visible CGI when the director does action shots with a moving camera.
Then, we have the powerful conclusion. One revelation made Natsuki gasp.
Basically, this is a good film. It doesn't quite fill its (short) run time, but it has a clear emotional vision and I'd feel more comfortable about recommending this to adults than the Smile film. (For small children, though, the Smile film is probably superior. It's wackier and has more action.)
And, as I said, I liked the ending.