One that I didn't realize was a YA novel is The Queen's Thief series by Megan Whalen Turner (
https://www.goodreads.com/book/show/448873 ) a top-notch series for me. I've also started reading the Old Kingdom series by Garth Nix, Sabriel is the first one, and it's not so obviously YA either. But the Percy Jackson and the Olympians series I would say fits your description, but they have a lot of humor in them which makes them ok. The other giveaway is the age of the central characters, and that there's nothing about sex, at best light romance.
But I agree with maddz that it depends on the author. A similar situation with me is how mystery novels rarely make me interested in the central character; they're typically 2-dimensional and there simply for the story. There are a few mystery writers who do a decent job of character development; Donna Leon being one, and Andrea Camilleri being another. I'm currently reading the 2nd mystery book by Chris Ould, the first one was decent.