Here's my perspective as a 20-year-old who first watched the show at the age of 15:
The Miraculous Ladybug movie left me disappointed due to its subpar writing and rushed pacing. Admittedly, condensing six seasons into a one-hour movie is challenging, but better planning and storytelling could have salvaged the experience. While the concept of exploring Marinette and Adrien's origin story and love arc was intriguing, the film suffered from too many narrative focuses, such as Marinette's bullying, a love triangle, and her personal growth journey. The film's downfall was exacerbated by cringe-worthy and overbearing songs that consumed a significant portion of the screen time, further detracting from the storyline. A major letdown for many Miraculous Ladybug fans, myself included, was the absence of Christina Vee, whose casting would have added authenticity to Marinette since she was the voice actress for the MBL series. Moreover, the portrayal of Adrien as a one-dimensional, love-stricken character was a disservice to his complexity in the series. Scenes like Adrien moping in bed to 'Careless Whispers' felt out of character and diminished his depth. The film missed the opportunity to showcase Adrien's multifaceted personality beyond his romantic struggles. Despite these flaws, the movie's saving grace lies in its commendable animation and artistic elements. However, these positives only partially make up for the overall disappointment caused by the movie's narrative missteps and questionable creative choices.