I remember watching the show when i was around 11 years old for the first time and it very quickly became one of my favourite shows. Now that I am 19 years old, I could say the show is still so perfect with an amazing plot, animation, characters and so on (at least from season 1 to 5).
I believe the show and the trailer had my expectations for the movie to be very high but it was kinda just disappointing. Sure the animation is great and everyone looks just like they did on the show but... the script was poorly written I believe. Like I am well aware a movie is way shorter than a 5 seasons show so it couldn't have been as detailed but I just still think it could've been better. Most fans of ladybug and cat noir are young adults by now so for the script to be idk childish was just not the move.
Why was it even a musical? I hate musicals to be honest but maybe I could've handled it if the singing voices were the same as the real actor's voices but Marinette did not even sound anything like herself and that made me cringe the entire time. So I had no other choice but to skip almost all of the songs. (I watched it in french so maybe the voices aren't as different when they're singing in english idk)
I really do wish cat noir/adrien was cooler like he is on the show. In the movie he kinda seemed like just a side character with boring/different lines. In a way, I didn't like how inaccurate the storyline was from how it really was on the show although maybe the last dance was comforting.
All in all, I didn't like the beginning (i wish they started it with all of them already great friends and not as if she was an outcast like how in the show the entire class basically loves her and gets along really well with her (they always have parties on a boat, comes to her house to play video games or tries on her new clothing designs) except for like Chloe and Lila). I also didn't like the plot where it was mostly all about Marinette getting over her fears and insecurities, especially since she never really acted like this in the show. Sure she has always been clumsy (especially around Adrien because he makes her nervous), but she was always brave and courageous and spoke up her mind so I just didn't appreciate how they kinda changed her to be weaker.