Many writers have turned to YA fiction because it is carefully crafted on all levels. Readers have discovered this, too. This has some “adult” publishing folks scurrying to figure out what is going on. Certainly, there are, um, insubstantial YA books, just as there are light reads for the adult market. Not every book aspires to be great literature. Some stories are just fun. Here’s an article about “New Adult” fiction. This is an emerging and controversial idea. Read the article and see what you think.
Why Not-So-Young Adult Readers Crave Teen Fiction – The Cut.
One Way to Wonder 
Yes, in fact, I think I had a post leading to that article. I write YA also, but the book I am working on right now is a middle grade. (I taught fifth grade for many years.)