I enjoyed this movie! Not saying that I'll be able to convince those who don't like it why they should, but I will try to explain this movie from the perspective of its target audience.
Very rarely do you get to see the interests of a teenage girl portrayed honestly on screen. Normally their antics are shown as completely cringy or played straight. I think Turning Red was able to show both the aspects of being a teenage girl pretty evenly. It's not as if Mei paraded around the school, showing her love for this boy band-- she did it with her friends and at home.
I think it's a shame that many people are missing out on the emotional heart of the movie. Yes, it's bad that she kept secrets from her mother, but because of their very one-sided, transactional relationship, she felt it best to do so. Very often strict parents find their children hiding more and more from them because they're unwilling to listen to their child's opinion. And it's not like the movie shows the conflict between Mei and her mother as her mother is completely in the wrong, we get to see Ming's perspective as well and the movie portrays her in a sympathetic light. It shows how the stresses you go through while being a child can affect you throughout adulthood, and I think it's a wonderful movie for kids and adults alike. Children should be aware of puberty, I don't know why people try to hide it, but I understand why people might want to save it for a seven-year-old instead of a five-year-old. Then again, it's not like I understood the majority of The Incredibles at age four.
Also yes, there are some parts that will make any socially conscious person cringe, but alas, that is what being a middle schooler is.
TLDR; Perhaps a movie saved for older children aged 7+, but overall a good movie that mixes Chinese culture, the late 90s, and being a middle schooler into a fun and heart-filled (mostly) easily digestible piece of entertainment.