SPOILERS AHEAD:
As a long-time Descendants fan, this movie left me disappointed and severely underwhelmed. Not only was the plot lackluster, but it was filled with plot holes. I was particularly unsatisfied with the climax of the film, and the overall conflict. During the climax of Descendants 1, 2 and 3, the protagonists battled a killer dragon, a powerful sea witch, and a girl cursed by Maleficent's power. These are truly life and death situations, or situations where an entire island of villains was about to be unleashed to the world. In Rise of Red, on the other hand, the climax was merely the protagonists trying to get a book from the principal's office? And even when the VK's show up, their appearance is very underwhelming, since they do not even seem intimidating or powerful. The movie attempts to make the main conflict seem like a life or death situation by showing that the Queen of Hearts kills Cinderella (which I thought was going a bit far for a kids movie), but that is merely a reason for the characters time travelling, and is not part of the climax itself. I feel like the movie makers just tried to make the Queen of Hearts a tyrannical and heartless killer as an excuse to give the movie somewhat of a conflict, but ended up creating a hollow storyline with absolutely no depth whatsoever.
I was also disappointed by the fact that the Castlecoming, a seemingly massive event in the school, was never actually shown in the movie. It was mentioned many times and was referred to as where Brigitte's life was ruined, but the characters travel back to their original time before the dance actually takes place. I feel like if they moved the climax further into the timeline, the plot would be somewhat better. The protagonists stopped the VK's before they actually had a chance to do anything, and this made the resolution extremely underwhelming, and left me empty. When the climax took place in the movie, I was surprised to see there was only about 12 minutes left. It just felt very unresolved. In most movies, the climax takes place at the 'tipping point' of the events, where the characters are about to lose everything, and clutch everything at the last second. The characters manage to save the day significantly before the 'tipping point', which results in a lackluster resolution.
The songs in this movie were atrocious, and are undeserving of the 'Descendants Songs' title. Not only did the songs feel like they took up the majority of the movie, but they were not catchy or pleasant to the ear at all. I found many quite obnoxious, with very badly written lyrics that did not flow well with the melodies. The songs also played at the most random moments in the plot, and felt like they did not fit in at that particular point in the storyline.
The sets in this movie also looked so cheap and so artificial, which broke the 'movie immersion'. In some scenes, especially in Wonderland and in the school courtyard, I could just tell I was looking at a plastic set with fake plants and fake bricks. The movie makers did not even try to make the set seem realistic, probably trying to cut costs.
In summary, this movie is a contrived and uninspired cash grab that is not worth your time.