It is a mistake to think of movies like Turning Red or any other movie as primarily a means of teaching a lesson. It is not. It is entertainment. That is the core purpose of movies. But there are many ways of entertaining. Some movies use humor, like the 20th century Warner Brothers cartoons. Movies that do teach a lesson do not so much teach as help the viewer realize something within themselves that was there all along. Sticking with Pixar, we can look at Soul, which teaches that we should appreciate the little moments of life and live every minute of it. Or Coco, which teaches the value of remembering our loved ones. But if that's all they did - teach a lesson - they would be big flops. People do not watch Soul or Coco to learn a lesson. They watch it to have their emotions taken for a ride. Good movies present characters in such a way that we grow to care about them. As
@RDKirk observed, movies can even make us care about a trash-compacting robot just as much as an eleven year old girl from Eden Prairie who moves to San Francisco. Usually, the characters we have grown to care about have a satisfying resolution. But not always. Take Grave of the Fireflies, an animated film from Studio Ghibli where the only characters we have grown to care about both die of starvation. Even that is entertaining in a sad sort of way. If movies teach a lesson, it is only as a side-effect and not the principle goal of the filmmakers.
That said, it is often the case that good movies do teach a lesson. As for Turning Red, people see lessons in it depending on where they are coming from. It may not even be a lesson that was envisioned by the director. I liked it because it subverts expectations. I was surprised to see Mei's three friends remain supportive the entire movie. A more hackneyed writing of the script would have made Mei totally isolated so as to increase the tension. Or they might have made Mei handicapped or a poor student or have a totally toxic relationship with her mother. But no. Mei had a reasonably good relationship with her mother and her mother really did care about her. There really was no stereotypical villain such as we saw in many of the early Disney movies. Everyone had a redemption arc - even Tyler, the school bully! This is satisfying entertainment, lesson or no lesson. We might say the characters in the movie learned lessons - not the viewers. We like to watch others learn lessons that we sort of knew and are being reminded of through the film.
I don't know if any of you watch "reaction videos", but this is a whole genre of YouTube videos made by all sorts of different YouTubers. There are reaction videos to just about any big name movie you might mention. In particular, there are a ton of reaction videos to Turning Red. These are supposedly made by the YouTuber watching the movie for the very first time and reacting to it with commentary along the way. Some are pretty good. Others are downright boring. But they do give a good window into what moves people in real time. It is very different from a carefully-crafted review made after watching a movie. In many of these videos, the YouTuber cries at certain scenes. This says more than any review. Anyway, I have watched a few reaction videos to Turning Red, and the places that gets the strongest reaction from the viewer are when Ming shows the drawings to Devon and others, when Mei is thrashing about in her empty cell of a room (so there won't be any more accidents), when Mei doesn't stand up for her friends accused by Ming of corrupting her after the Tyler party, when Mei's friends and 4Town join the chant at the Sky Dome, and when Mei comforts a young Ming in the bamboo forest. Just go to YouTube and search for "Turning Red reaction".