I've been seeing a lot of this on my timelines and FYPs lately.
"If the OG cast isn't in it, I'm not watching"
"This is so disrespectful"
"Descendants stopped at D3"
And while I understand it, I think a lot of it is misguided by the fandom. First off, continuing a franchise/series even after a character has passed isn't anything new. I mean, Paul Walker was a major character in the Fast and Furious Franchise, but even after his death, they still went on to make 5 more films, with a 6th film in production right now and coming out next year. Continuing a franchise even after a major character's death isn't something new to the film industry.
Had they tried to replace Carlos's actor with someone new to continue on the story of Mal, Jay, Carlos, and Evie, then I could see the argument that it's disrespectful. But they're not trying to continue on Mal, Jay, Carlos, and Evie's story anymore.
Something I think a lot of people are doing is trying to pull in Descendants: Rise of Red and Descendants: Wicked Wonderland as sequels to the original 4 VK's story, and these films were never designed to be a continuation of the original 4 VK's story. Their story has already been told.
Disney always made it clear Descendants: Rise of Red was designed to be a spin-off, not a continuation of the original VK's story. The Royal Wedding Special was the finale to Mal, Jay, Carlos, and Evie's story, but it was also a passing of the torch to the next generation of VKs who would be taking center stage in a spin-off. It was always supposed to be about a new VK: Red and her story.
So yeah, if you don't want to watch Red's story, fine. You have 4 books, 3 movies, an animated series, and an animated special to relive Mal, Jay, Carlos, and Evie's story all you want. But I'm tired of seeing people trying to use Red's story as a continuation of a story that's already been finished as an excuse to bash the new films or to criticize the new cast.