A film based on a popular animated series in French, as someone who is not familiar with the lore, it felt very compact, easy to digest and had a good time watching it.
In terms of the cast, obviously, Ladybug / Marinette and Cat Noir / Adrien are the ones that carried the film whole through. Through sequences and their actions, Marinette is shown to be a shy and clumsy girl who continues to doubt herself due to her fears. And as the film progressed, it's very easy to connect with her. As for Adrien, he is charming and relatable because he too also has personal problems but related to his father. Knowing that they are the core of the movie, it is no doubt that they are filled with personalities and you can't help but feel their pairing - and they are made for one another. So long as they believe and work together, nothing can really stand in there way and that's what makes them worth rooting for - from teamwork, friendship and eventually love.
When it comes to the genre aspect of the film, the musical, for the most part, was surprisingly good. Granted, considering the original series was not, some may find it corny at times. But this reviewer found it to be really great to listen to. Out of the eight songs played in the film, seven if not including the show's theme song, three stood out as the best. Two were solos, one by Marinette and the other by Adrien and the third one when they sang it as a duo - which was very romantic. There is this one song though, that is so popular, it was so surprising that it was used in the film.
Animation-wise, unlike the series that has not-so-fluid animation, considering that it is a feature-length film, it is more smooth to look at alongside the voice acting that was really great as expected.
As for the story, it was able to flesh out the characters and didn't really need a lot of exposition to do so. Even though the film feels very rushed in order to get from point A to B, it's really hard not to enjoy the ride. Just to add, there were certain sequences, particularly in the second act, that felt very similar to other films such as Smurfs 2, Ghostbusters (2016) and Hercules - if you see it then you will understand. It's also nice to mention the Sailor Moon vibes such as the transformation as well as the typical villains. The final act, while it could have been a lot better and impactful, felt satisfying by the end. It could have stopped there but seems like there are plans for another film.
Overall, it's hard for this reviewer to dislike the film. It was fun, charming and an innocent film. Despite its cheesiness, the core of the film, Marinette and Adrien, just made the movie work because of their friendship and romance. As someone who is just a casual fan or have little to no idea about the lore at all, it was a really good time watching Miraculous: Ladybug and Cat Noir, The Movie.